ABSTRACT

Great Salt Lake is recognized regionally, nationally, and

hemispherically for its extensive wetlands, and its tremendous and often unparalleled values to migratory birds. These

values are derived from the lake’s unique physical features,

including its immense size, dynamic water levels, diversity

in aquatic environments, extensive wetlands, and geographic

position in avian migration corridors. These features create a

mosaic of habitat types that are attractive to literally millions

of migratory birds that use the lake extensively for breeding,

staging, and in some cases, a wintering destination. Great

Salt Lake also has a rich history of wildlife management

activities that were initiated in the late 1890s by private hunting clubs, but were followed by substantial state, federal,

and private investments in conservation programs. More

recently, agency activities have focused on improving our

understanding of migratory bird abundance and ecology, and

development of cooperative, comprehensive, and integrated

management strategies for lake resources. In spite of historical and contemporary conservation activities, the migratory bird resources of Great Salt Lake remain vulnerable to

threats from a myriad of natural and anthropogenic factors.

The management challenges to sustain migratory bird

resources during the 21st century will only increase as competition for lake resources increases.

INTRODUCTION 

Great Salt Lake (GSL) is rich in a number of natural

resources, most notably its abundant minerals, a unique brine

shrimp population, and a diverse and abundant migratory

bird population. The lake has also been heavily utilized for

the recreation, open space, and tourism opportunities it

offers. As demands on the lake’s natural resources have increased, so has the need for information necessary for making wise management decisions that will sustain those natural resources into the new millennium. This paper compiles

recent data on migratory bird populations using the lake,

which can serve as a general reference for interested parties

and decision makers. Our intent is to not only enumerate

migratory bird resources, but to convey the significant ecological role GSL plays in North American and hemispheric

bird conservation. Much of the information provided is derived from recent unpublished Utah Division of Wildlife

Resources surveys, but we also include general summaries

from other authors where we felt a historical perspective is

important to the reader.

GREAT SALT LAKE ECOLOGICAL SETTING

Physical Setting and Its Relationship to

Wildlife Habitat

The physical dimensions, geographic setting, geology,

and climate of GSL are described in great detail elsewhere

(Gwynn, 1980). This article briefly discusses GSL area as it

influences bird life associated with the lake. The scale of the

ecological setting is immense. The entire system occupies

roughly 3,011 mi2 (7,800 km2), consisting of lake, uplands,

wetlands and drainage stems. Birds use all of these areas

year-round.

Climate

GSL sits in a cold desert environment with summer and

winter temperatures often reaching 100°F (38°C) and 0°F

(-18°C), respectively. The lake area receives an average of

15 inchs (38 cm) of moisture in the vicinity of the Wasatch

Front and less than 10 inchs (25 cm) on the west side of the

lake.

AVIAN ECOLOGY OF GREAT SALT LAKE

by

Thomas W. Aldrich

Utah Division of Wildlife Resources

1594 West North Temple

Salt Lake City, Utah 84116-3154

nrdwr.taldrich@state.ut.us

and

Don S. Paul

Utah Division of Wildlife Resources

515 East 5300 South

Ogden, Utah 84405

avocet@utah.uswest.net
344 Utah Geological Survey

Hemispheric Setting

GSL is one of several terminal lake systems in the Great

Basin and is the fourth largest terminal lake in the world

(Stephens, 1997). With its impressive size and extensive associated wetlands, the presence of GSL, in an otherwise xeric

environment, underscores the “oasis” effect of the system.

Consider the lake's position in the western hemisphere.

There is a broad sweep of land that lies between the Cascade

Mountains and the Mississippi River valley extending from

the arctic rim to nearly Central America that receives less

than 20 inches (50 cm) of precipitation annually. Except

mountain environments, this is a vast arid region of the

Americas. In this setting, productive sites for feeding, fattening, and molting of large numbers of migratory birds are

isolated and often vast distances apart. These sites are always the exception and not the dominant habitats. From

breeding grounds in the arctic, many species of birds travel

more than 1,860 miles (3,000 km) by the time they arrive at

GSL. Some will need energy to travel farther south to reach

their wintering grounds. An American avocet (Recurvirostra

americana) travels approximately 1,300 miles (2,100 km) to

winter on the west coast of Mexico at Marismas Nacionales.

A Wilson’s phalarope (Phalaropus tricolor) doubles its

weight on GSL brine flies (Ephydra cinerea) and brine

shrimp (Artemia fransiscana) before flying nonstop, nearly

5,400 miles (8,800 km), to Laguna mar Chiquita in central

Argentina. Other species migrate as near as the Salton Sea

or as far as the Straits of Magellan from GSL.

GSL Ecological Setting

There are some notable physical features of the GSL

region that are particularly important to birds and other

wildlife; many are natural, while others are constructed (figure 1). The close proximity of GSL to the Wasatch Range

and the riverine environments of the Bear, Weber, Ogden,

and Jordan Rivers, and other smaller drainages plays a principal role in the local ecology. The terminal nature of the

lake, with its various saline systems and associated

halophiles, contributes greatly to the uniqueness of its natural wonders. GSL is a playa lake with an extremely low-gradient bottom. When its surface elevation is 4,202 feet

(1,280.8 m) above sea level, the average depth of the lake is

13 feet (4 m). With the seasonal recharge of water from

rivers and other drainages, and the subsequent evaporation,

the effect of this shallow flat bottom is most apparent in the

highly transitory shoreline. This results in ephemeral pools,

expansive mud flats, and sand bars that warm quickly in

spring, and easily reach temperatures around 84°F (29°C) in

summer. Some parts of the lake shoreline migrate more than

880 yards (805 m) from spring to fall depending on the water

and evaporation year. These water depths and shoreline fluctuations are fundamental ingredients in the creation of highly productive habitats for wading waterbirds.

All associated systems (bays, wetlands, etc.) are dominated by alkaline soils. The major ions in GSL’s chemistry

are sodium and chlorine. The associated plant community

consists primarily of halophytes, many of which must stand

the rigors of inundation and desiccation. The wetlands associated with these plants are usually lacustrine, sometimes

modified by riparian systems, wet meadows, mud bars, sand

beaches, and playas. There are brackish- and fresh-water

marshes located within the systems dominated by fresh water

hydrophytes. GSL drainage structure is sediment driven

(Gwynn and Murphy, 1980). Clastic sediments comprised of

fine-grained material, are deposited in bay areas of the lake

(for example, Bear River Bay, Ogden Bay and Farmington

Bay). Some of these form into baymouths, bars, alluvial

fans, and crowfoot deltas. These landforms provide an ideal

substrate for interspersed wetland vegetation, thus generating

habitat edge, and sites for colonial nesting birds.

Within the GSL basin there are essentially four water

regions with differing ecologies. These regions are Bear

River Bay, Farmington Bay, the Gilbert Bay (southern arm)

and Gunnison Bay (north arm) (figure 1). The major difference between these regions is salinity, although there are

other features that play roles in defining their ecological peculiarities.

Bear River Bay is the freshest region and receives the

largest volume of riverine inflow. Its near-surface salinity is

similar to that of the Bear River. This system is bounded on

the north and east by state, federal, and private wetlands; on

the south by industry; and to the west by the Promontory

Mountains. This bay is fresh enough to support a community of submergent hydrophytes including sago pondweed

(Potamogeton pectinatus) and widgeon grass (Ruppia maritima). There are also significant islands of emergent wetlands here, especially in the east part of the bay in the Willard

Spur (figure 1). An ecological element of vital importance to

pisciverus birds in this area is the fishery that persists when

the lake elevation is higher than 4,200 feet (1,280.2 m) above

sea level. The avian community at Willard Spur is exceptionally complex. With its species richness, diversity and

overall abundance, this area continually provides one of the

most magnificent displays of bird life on the lake. Although

the smallest region on the lake, it makes an exceptional contribution to the lake’s avian population.

Farmington Bay is the next freshest region, with a salinity of approximately 60 parts per thousand (ppt) when GSL

is at 4,200 feet (1,280.2 m) above sea level. It does not provide a submergent vegetation community due to the elevated

salinity, but has a relatively complex plankton community

compared to the south and north arms of the lake. It supports

some important halophiles (for example, brine flies) in conjunction with some macroinvertebrates that tolerate diluted

brine environments, but it is too saline to support a fishery.

There is a significant wetlands influence in this region, often

modified by the associated transitory shoreline, especially in

the Layton/Kaysville Marsh area (figure 1). This effect is

also visible at the south end of the bay, west of Farmington

Bay Waterfowl Management Area (WMA). The open-water

reaches of this region are an important waterfowl habitat in

late fall and winter. The shorelines are important to breeding

and migrating shorebirds.

Farmington Bay is bounded on the west by Antelope

Island, to the north by the Antelope Island causeway, and to

the east by extensive wetlands, including Nature Conservancy property and those of Farmington Bay WMA. The south

boundary is formed by an extensive shoreline with portions

controlled by the State, duck clubs, private ranching, and the

National Audubon Society. A part of this shoreline has been

developed into the southern causeway to Antelope Island.

Gilbert Bay (south arm) of GSL is the largest reach of

water on the lake, with a salinity of 100 to 140 ppt at 4,200
Great Salt Lake - An Overview of Change 345

feet (1,280.16 m) above sea level. At this salinity, the lake’s

chemical and biological properties eliminate most in-lake

predatory influences (predatory macroinvertebrates, fish,

etc.) on the obligate halophiles (for example, brine shrimp

and brine flies). These macroinvertebrates flourish under

ideal conditions (especially at salinities in excess of 120 ppt),

producing millions of pounds of potential protein for birds

that have special behaviors or adaptations to exploit this food

source. The lake can be unusually productive; during one

study, the average production of brine fly biomass was 7.9

g/m2 (Collins, 1980). During some harvest seasons, the brine

shrimp industry removes more than 13.9 million pounds (6.3

million kg) of brine shrimp cysts and detritus from Gilbert

Bay ( south arm).

The south arm contains several islands crucial to colonial nesting bird species. Among the four water regions of

the lake, the south arm has the most variable levels of salinity, especially near points of fresh water discharge. The

south arm is framed by the Southern Pacific Railroad

causeway and Promontory Point to the north; the Lakeside

Mountains to the west; and the Weber

River wetlands, Antelope Island. and

the Jordan River delta to the east. The

south shore of GSL and Stansbury Island are the main geographic features

forming the south arm’s southern

boundary. Here natural areas are interspersed with mining and mineral

industries, and the railroad causeway.

Gunnison Bay is the second largest expanse of open water. The north

arm is bounded by salt playas and the

Locomotive Springs WMA on the

north; by the Promontory Mountains

on the east; by the Hogup Mountains

on the west; and by the Southern Pacific Railroad causeway on the south. It

is also the most remote and xeric region of the lake and, perhaps more

importantly, the most saline. Salinity

ranges between 240 and 280 ppt.

Gilbert Bay is presently a hypersaline

system dominated by halophytic bacteria; it is too salty for brine shrimp

and brine flies to persist. Currently, it

appears to be a salt trap with possibly

3 to 5 vertical feet (1 to 1.5 meters) of

salt precipitate on the lake floor. It

possesses several minor wetlands that

function to support small populations

of unique birds. Gunnison Island has

provided a nesting habitat for an

impressive number of American white

pelicans (Pelecanus erythrorhynchos)

and California gulls (Larus californicus) before, and since settlement of the

area by Anglo-Americans. For birds

choosing to nest on this remote island,

the tradeoff is a predator-free nesting

environment for marathon flights to

forage and gather food for young.

Life forms that persist in these

GSL environments as residents or tranFigure 1. Map of Great Salt Lake and notable features associated with the lake important to waterbird life.

American white pelican adults and young find refuge on Gunnison

Island - the only current pelican colony in Utah and one of the largest

and most protected in North America.
346 Utah Geological Survey

sients must do so under harsh and extreme conditions, with

seasonal temperature variances exceeding 100°F (38°C),

whimsical moisture cycles, and adjacent to brine-laden waters. Many organisms which survive such conditions, especially plankton, have evolved to be seasonally productive

and reproductively flexible. Many avian species pattern their

arrival, breeding, nesting, and departure times around these

seasons of high macroinvertebrate productivity to take advantage of the unique food chain provided by GSL.

Numerous birds utilize the nearby wetlands and uplands

associated with GSL. The proportional use is determined by

the species, time of year, and current environmental conditions. Some species use only certain elements of the ecosystem. For instance, tundra swans (Cygnus columbianus) are

dependant on submergent vegetation and rarely frequent

GSL; northern shovelers (Anas clypeata) use both the lake

and wetlands; and common goldeneyes (Bucephala clangula) rely heavily on the open lake environment. Understanding habitats and habitat relationships of avian species in

the ecosystem is vital in this discussion.

Habitats

In addition to the lake regions listed in the Ecological

Setting section of this article, there are many critical and

important habitats. Several of these are discussed here.

Wetlands

The wetlands of GSL have long been recognized for

their importance to migratory birds. Journal accounts of

explorers, as well as market hunters, at the turn of the 19th

century reflect some of the earliest written descriptions of

these wetland resources and their associated wildlife. More

recently, the importance of GSL wetlands has been formally

recognized in numerous local, international, and hemispheric planning and management efforts.

In spite of the long-standing acknowledgment of GSL

wetland importance, quantification and classification of

these wetland resources are imperfect. Jensen (1974) summarized Utah wetland resources based on criteria reflecting

their importance to waterfowl. He accounted for approximately 558,000 acres (225,822 ha) of wetlands statewide,

with about 85 percent (474,139 acres; 191,884 ha) occurring

around GSL (table 1). Photographic coverage of GSL, as

part of the U.S. Fish and Wildlife Service (USFWS) National Wetland Inventory (NWI), was conducted in 1981, but

coverage of GSL is incomplete. Several concurrent efforts

by various agencies are underway to classify and quantify

wetland resources within their jurisdictions using NWI data,

but as of this writing, no published summary of lake-wide

wetland resources by wetland class is available.

The nature, location, and extent of GSL wetlands are

driven largely by two factors; the availability of fresh water

and the surface elevation of GSL. Because GSL is a terminal basin of ancient Lake Bonneville, salts have accumulated

in it since prehistoric times. Because of this, the sediments

and water of the current lake bed are highly saline and cannot support vascular plants. Wetland plant communities are

therefore distributed where precipitation, surface inflow, and

ground-water discharge are sufficient to freshen sediments

and allow for plant germination, growth, and reproduction. 

Stauffer (1980) modeled the water budget for GSL and

estimated an annual fresh water supply to the lake of

3,250,000 acre-feet (4,007 hm3). From this, surface water

flow, precipitation, and groundwater discharge account for

65 percent, 28 percent and 8 percent, respectively, of total

fresh water inflow. Of the surface flow, the Bear River supplies the greatest amount of water (55 percent), followed by

the Weber River (23 percent) and the Jordan River (14 percent). Ungaged flows from sewage plants and other small

tributaries account for the remainder of surface inflow (8 percent). Wetlands of GSL are associated mainly along the

deltas of these major rivers, with smaller and more isolated

wetland complexes located near drains and small tributaries

and ground-water discharge areas at Locomotive and Timpie

Incubating pelicans at Gunnison Island. During this period, each

adult spends an average of 72 hours at the nest before being relieved

by the other parent. When the young hatch, each adult takes a turn airlifting fish from fresh-water sites to feed the young. The closest fishery, Bear River Bay, is 30 miles distant.

Table 1. Wetland acreages and estimated water needs of the Great Salt Lake (Jensen, 1974).

County 1st Magnitude 2nd Magnitude 3rd Magnitude Total Annual Water

Marsh Marsh Marsh Marsh Needs (Acre-feet)

Box Elder 188,465 53,188 17,000 258,653 800,641

Davis 96,886 — — 96,886 502,471

Salt Lake 25,130 2,560 7,780 35,470 103,163 

Tooele 1,440 — 7,640 9,080 48,657 

Weber 28,122 8,903 37,025 74,050 88,928 

Total 340,043 64,651 69,445 474,139 1,543,860
springs. Although relatively small in proportion to river

flows, precipitation plays an important role in freshening

sediments on small playas and mud flats that are removed

from other sources of fresh water.

Given that fresh water is essential for wetland persistence, the factor that potentially limits the distribution and

extent of wetlands is the surface elevation of GSL. GSL elevations are extremely dynamic and change in response to

long-term precipitation cycles, seasonal changes in evaporation and inflow, and daily influences from wind-driven seiches. Since 1851, the surface elevation of GSL has varied more

than 20 feet (6 m) from a low of 4191.4 feet (1,277.5 m)

above sea level in 1963 to a high of 4211.8 feet (1,283.8 m)

in 1986 and 1987. These extremes produce a change in the

surface area of GSL of approximately 872,000 acres

(352,898 hm2) (table 2) which more than doubles its size

(Cruff, 1986). The relative change is even more pronounced

along the eastern shore of GSL, where differences in surface

area change more than 21-fold between lake elevations of

4191 and 4205 (1,277.4 and 1,281.7 m) (Waddell and Fields,

1977). The most dramatic example of impacts from longterm lake level fluctuations was the flooding of the 1980s

when an 11-foot (3.4 m) rise of GSL occurred over a four

year period. The lake inundated approximately 80 percent of

GSL wetlands with brines, killing essentially all vegetation

and many tuber and seed banks. Flooding resulted in more

than $30 million of damage to State-managed facilities.

Lake-wide waterfowl use and production also declined 80

percent to 90 percent.

Seasonally, GSL levels change in response to evaporation and inflow producing an annual high during May-July

and a low during October-November. On average, the historical seasonal difference in GSL elevations is 18 inches

(0.46 m) but has changed as much as five feet (1.5 m) in one

year. On average, each foot of change in GSL elevation

changes the surface area of GSL by nearly 44,000 acres

(17,807 hm2) lake-wide, and approximately 17,500 acres

(7,083 hm2) along the eastern shore (table 2). However,

changes in the surface area in response to lake levels are not

uniform. The greatest change in surface area for any given

change in lake level is between lake elevations of 4,195 and

4,200 feet (1,278.6 and 1,280.2 m). Winter and spring increases in GSL elevations therefore result in inundation of

tens of thousands of acres with brine in most years, and hundreds of thousands of acres in exceptionally wet years. 

Wind-driven seiches also have dramatic impacts on GSL

elevations. “The magnitude of the setup on the speed, direction, fetch, depth of lake at that point, and direction of the

Great Salt Lake - An Overview of Change 347

Table 2. Surface area of the Great Salt Lake relative to lake elevation (Cruff, 1986).

GSL Surface Area (Acres) Change in Surface Area/Foot Elevation

Elevation North Arm South Arm East Shore GSL North Arm South Arm East Shore GSL

4191 221,200 378,900 12,000 600,100 8,200 12,100 2,861 20,300 

4192 229,400 391,000 14,861 620,400 8,300 12,200 5,285 20,500 

4193 237,700 403,200 20,146 640,900 19,600 22,200 9,092 41,800 

4194 257,300 425,400 29,238 682,700 19,700 22,400 19,336 42,100 

4195 277,000 447,800 48,574 724,800 21,600 40,200 23,530 61,800 

4196 298,600 488,000 72,104 786,600 21,700 40,200 24,025 61,900 

4197 320,300 528,200 96,129 848,500 21,600 40,300 24,738 61,900 

4198 341,900 568,500 120,867 910,400 21,600 40,200 24,572 61,800 

4199 363,500 608,700 145,439 972,200 21,700 40,200 29,150 61,900 

4200 385,200 648,900 174,589 1,034,100 15,100 21,300 25,411 36,400 

4201 400,300 670,200 200,000 1,070,500 15,200 21,200 18,000 36,400 

4202 415,500 691,400 218,000 1,106,900 15,200 21,300 14,000 36,500 

4203 430,700 712,700 232,000 1,143,400 15,200 21,300 10,000 36,500 

4204 445,900 734,000 242,000 1,179,900 15,200 21,300 14,968 36,500 

4205 461,100 755,300 256,968 1,216,400 12,200 18,200 30,400 

4206 473,300 773,500 1,246,800 12,300 18,300 30,600 

4207 485,600 791,800 1,277,400 12,200 18,500 30,700 

4208 497,800 810,300 1,308,100 12,200 69,400 81,600 

4209 510,000 879,700 1,389,700 7,300 28,900 36,200 

4210 517,300 908,600 1,425,900 7,200 15,700 22,900 

4211 524,500 924,300 1,448,800 7,400 15,900 23,300 

4212 531,900 940,200 1,472,100 40,800 53,300 94,100 

Average 15,977 27,936 17,498 43,914 
348 Utah Geological Survey

wind. Wind setup exceeding two feet is not uncommon....

The combined effects of wind setup and high waves (wave

runup) can produce adverse impacts to elevations five to

seven feet above the static lake elevation” (Utah Department

of Natural Resources, 1999). These events can push brines

onto tens of thousands of acres of mud flats and into emergent marsh areas, and de-water similar acreage on the

upwind side of the lake. These events tend to be short lived,

however, and normally do not impact established vegetation.

Unlike seasonal and long-term changes in GSL levels, wind

seiches are accompanied by heavy wave action that can

erode shorelines and greatly disrupt sediments. As a consequence, seed germination and plant establishment along lake

boundaries can be hindered and, in some cases, prevented by

frequent wind events. In extreme cases, established vegetation can be uprooted by heavy, sustained wave action. 

Breeding birds that construct nests on mud flats, floating

vegetation or emergent cover near water surfaces can also be

impacted by wind seiches. Shorebirds, ibis, grebes, geese,

and diving ducks are examples of species groups whose nests

are commonly destroyed by wind-generated flooding. These

impacts are not restricted to the open body of GSL, since

many of the larger impoundments on management areas also

experience wind tides. 

Whereas the boundaries of wetland plant communities

around GSL are limited by sediment and water salinities,

species composition within wetland environments is influenced by plant tolerances to salinity, hydroperiod and water

depth. Christensen and Low (1970) demonstrated that most

common wetland plants found within GSL basin germinate

and grow best in fresh water, but differences in salt tolerance

among plants exist. As a consequence, fresh water areas

around GSL tend to be dominated by the most aggressive and

competitive plant species while more salt-tolerant plants occupy the brackish areas. Among submersed aquatic species,

widgeon grass and muskgrass (Chara spp.) are most salt tolerant, while sago pondweed and horned pondweed (Zannichellia palustris) are slightly less tolerant. Among emergent species, alkali bulrush (Scirpus paludosus) and Olney’s

bulrush (Scirpus olneyi) are most salt tolerant, while cattail

(Typha spp.) and hardstem bulrush (Scirpus acutus) tend to

be restricted to fresher environments. 

These differences in salt tolerance, in part, explain the

general patterns in wetland plant distribution around GSL.

Wetlands associated with the freshest riverine inflows (Jordan, Weber and Bear Rivers) tend to be dominated by cattail,

sago pondweed, and hardstem bulrush. Wetlands fed by higher salinity inflows (Salt Creek, Locomotive and Timpie

Springs) or are located below impoundment dikes or along

the lake shore interface, tend to be occupied by widgeon

grass, chara, alkali and Olney’s bulrush.

Uplands

Similar to GSL wetland habitats, upland communities

are extensive and geographically vary throughout the GSL

basin. Rawley (1980) described and mapped these communities so details will not be provided here. In general,

uplands of GSL on the south, west and north shores tend to

be dominated by shadscale (Atriplex confertifolia)-greasewood (Sarcobatus spp) associations adjacent to barren or

sparsely vegetated salt flats and beaches. Combined with little to no fresh water, these upland areas provide relatively

less benefit to migratory birds. Uplands along the east shore,

however, are closely associated with expansive wetlands,

due to greater annual precipitation and runoff, deeper soils,

and extensive irrigation systems. Although some greasewood and sagebrush (Artemisia spp) persist along benches,

upland communities are made up of more numerous grasses,

forbs and shrubs with higher wildlife values. Extensive agricultural areas are also present, with cereal grains and alfalfa

being the predominant crops.

Upland areas along the east shore serve several important migratory bird functions. They provide cover for upland

nesting birds, including several species of dabbling ducks,

Canada geese (Branta canadensis moffitti), long-billed curlews (Numenius americanus), and willets (Catoptrophorus

semipalmatus inornatus). Rank and dense upland shrub

cover is preferred by late-nesting species such as gadwall

(Anas strepera), while salt grass and other short-stature

plants are used by cinnamon teal (Anas cyanoptera). Upland

areas do not need to be close to wetlands to provide valuable

cover; as some species, most notably pintails (Anas acuta),

nest in areas up to a mile away from water. 

Natural upland areas provide substantial food resources

for a host of species. Canada geese graze extensively on

high-protein young shoots from a variety of wild grasses.

Seeds and invertebrates from upland plants that are backflooded during late summer and fall in managed impoundments are also important food resources, particularly to fall

migrants.

Agricultural areas on state WMAs, as well as private

lands, are used extensively by migratory birds. Canada geese

and greater sandhill cranes (Grus canadensis tabida) graze

heavily on fall and spring-seeded cereal grains and alfalfa.

Waste grain in harvested fields is used by several species.

Flood irrigated pastures provide enhanced access to both

invertebrates and small rodents during summer for a variety

of birds. White-faced ibis (Plegadis chili) and Franklin’s

gulls (Larus pipixcan) are commonly seen in flocks of hundreds exploiting flooded agricultural fields.

Upland habitats along the east shore are also tremendously important in buffering wetland areas and dependent

wildlife from disturbances and activities on adjacent lands.

High residential populations, much of the commercial and

industrial use, a web of transportation facilities including

rail, interstate highway and airport facilities, all exist within

the narrow corridor between the Wasatch Range and GSL.

Most future municipal- and county-planned expansions are

also confined to this limited area. Noise, free-roaming pets

and a host of other human activities can reduce the wildlife

values in wetlands, and upland buffers can reduce these

impacts and provide protection from future encroachment.

Islands

Nine islands on GSL have significant bird habitat values.

These islands are Antelope, Hat, Carrington, Egg, Fremont,

Gunnison, Landing Rocks, Stansbury, and White Rock (figure 1). These habitat values change with lake volume and

elevation. Most islands are accessible by land at low lake

elevations, and conversely, are covered or compromised by

water at high lake elevations. Of these islands, five are currently colonial nest sites and were this way in the past (Behle,

1958; Rawley, 1976). These islands range in size from 2,821

acres (1,142 ha) at Antelope Island to less than 1.2 acres (0.5
Great Salt Lake - An Overview of Change 349

ha) at White Rock. Some of these islands persist as colonial

nest sites through time regardless of historical fluctuations in

lake elevation. Others are used intermittently, due mostly to

topographic characteristics or disturbance from predators or

man. Some islands are comprised simply of Precambrian

rock with some soil substrate and sparse vegetation, while

others are heavily vegetated with shrubs, forbs and grasses.

Consistent colonial nesting species of the island environments are California gulls, great blue herons (Ardea haeredes), double-crested cormorants (Phalacrocorax auritus),

American white pelicans, and Caspian terns (Sterna caspia).

Even though they are not considered colonial nesting

species, the Canada goose and some duck species nest within, or near, colonial nesting sites on some of the islands.

Insulation from terrestrial predators is, in part, why colonial nesting species choose islands for nesting and rearing

young (Connell, 1975). However, some colonial species

have nested in large numbers on the GSL islands that have

well-established populations of coyotes (Canis latrans), bobcats (Felis rufus), and badgers (Taxidea taxus). This is an

exception for most sites when the lake is 4,202 feet (1,280.8

m) above sea level or higher as water levels prevent access

of most land predators.

The islands of GSL provide other habitat values to birds

in addition to nesting. For example, Gunnison Island was

found to be used for foraging and resting by 110 different

species between 1972 and 1974 during a study of American

white pelicans (Knopf, 1975). Fremont and Antelope Islands

provide thermal and uplift draft for pelicans, assisting them

in energy conservation as they travel to and from foraging

locations. The peninsula of the Promontory Mountains,

along with these two islands, are used by migrating raptors.

Many islands provide extensive shoreline for waterbird foraging and nesting.

Bars, mud flats, and hummocks are important substrates

for colonial species for nesting, loafing, and foraging,

although they are not islands. During years of low lake elevation (<4,200 feet (<1,280.2 m) above sea level), an impressive number of gulls and shorebirds are raised on these natural structures. These structures are a phenomena resulting

from the low-gradient lake bottom. Dikes, levees and other

manmade structures have become important habitat components to colonial nesting species on the lake. Many have

been partly responsible for the expanding population of

gulls. These structures could be considered artificial islands.

Dikes are crucial nesting substrates for gulls when lake elevations are higher.

GSL WATERBIRD ECOLOGY AND BIOLOGY

Waterfowl 

Waterfowl, for the purpose of this discussion, include

ducks, geese, and swans, which taxonomically form the family Anatidae. Worldwide, there are believed to be more than

160 species of waterfowl, with 50 species occurring in North

America. 

As a group, waterfowl are incredibly diverse in structure, size, physiology, and behavior. These characteristics

are responsible for a strong presence of waterfowl in Utah

and their ability to exploit the diversity of habitats available

in and around GSL. Thirty-five species of waterfowl are

known to use the lake and its periphery, although their timing of use, distribution, and abundance varies considerably

among species (table 3), seasons, years, and varying GSL

elevations. Although GSL is recognized mostly as a waterfowl migration corridor, many species are found in abundance during the summer breeding and molting periods, as

well as in winter.

Waterfowl Migration

Due to their classic chevron flight patterns, large flock

sizes, and frequent vocal arrival, migrating waterfowl are

often signals for changing seasons. Waterfowl use of GSL

occurs throughout the year, but populations are highest during migrations in late summer, and again in spring. Recent

population surveys on state WMAs and the Bear River

Migratory Bird Refuge (BRMBR) indicate that waterfowl

Table 3. Waterfowl species and their abundance during different times on the Great Salt Lake (unpublished data, DWR files).

Species Breeding Migration Wintering

Tundra Swan N C C

Trumpeter Swan N R R

Greater White-fronted Goose N R O

Snow Goose N C O

Ross' Goose N C O

Brant N O O

Canada Goose C C C

Wood Duck R R R

Green-winged Teal N C C

American Black Duck N O O

Mallard C C C

Northern Pintail C C C

Blue-winged Teal U U U

Cinnamon Teal C C U

Northern Shoveler C C C

Gadwall C C C

Eurasian Wigeon N O O

American Wigeon O C C

Canvasback U C U

Redhead C C C

Ring-necked Duck O C U

Greater Scaup N R R

Lesser Scaup O C C

Harlequin Duck N O O

Oldsquaw N O O

Black Scooter N O O

Surf Scooter N O O

White-winged Scooter N O O

Common Goldeneye N C C

Barrow's Goldeneye N U U

Bufflehead N C C

Hooded Merganser N O O

Common Merganser N C C

Red-breasted Merganser N O O

Ruddy Duck C C C

N=Not known to be present

C=Common (Found consistently in fair numbers)

U=Uncommon (Found occasionally in small numbers in appro priate habitat)

R=Rare (Found infrequently but regularly in very small numbers in proper habitat

and season)

O=Occasional (Seldom found in state and not reported annually)
350 Utah Geological Survey

begin arriving from northern breeding areas in June and peak

in September (figure 2). Banding studies have shown that

Utah receives most of its migrating ducks from the northwestern and mid-continent breeding areas in Alaska and

Canada, but some exchange of birds with other breeding

populations does occur. Ducks migrating through GSL predominately winter in California and the west coast of mainland Mexico, but some species, such as redheads (Aythya

americana) and cinnamon teal, can reach the coast of Texas,

and Central and South America (Bellrose, 1976). Greenwinged teal (Anas crecca) and pintail are the first migrants to

arrive, followed by shovelers, wigeon (Anas americana),

gadwall, mallard (Anas platyrhynchos), and canvasback

(Aythya valisineria). Mergansers and sea ducks, including

bufflehead (Bucephala albeola), goldeneye, and scaup (Aythya affinis), are the last to arrive in November. Cinnamon

teal are among the first ducks to leave Utah, with the majority gone by the end of September.

Populations begin returning from southern wintering

areas in February and peak again in March. The spring

migration period through GSL is markedly shorter and peak

populations substantially lower than in the fall.

Although current surveys suggest nearly 700,000 waterfowl are present in the GSL area in September (figure 2), this

number does not include populations of birds on many unsurveyed public and private lands. It also does not account for

population turnover during the migration period and movement of waterfowl off surveyed areas in response to hunting

seasons. Population counts on management areas are therefore a gross underestimation of true populations of waterfowl

migrating through GSL. Because GSL is positioned in a

major migration corridor between the mid-continent prairie

breeding areas and major wintering areas in California,

impressive numbers of waterfowl pass through Utah annually. Bellrose (1976), using several sources of information,

estimates 3 to 5 million ducks pass through GSL each year.

Migrating waterfowl prefer large, open marshes that are

free from disturbance. Key areas that offer these features include impoundments on state and federal management areas,

private hunting clubs, and the fresh water areas in Willard

Spur, Bear River Bay and the Layton/Kaysville marsh. Once

hunting seasons begin in October, waterfowl make extensive

use of shallow brackish areas along the GSL shoreline and

salt water areas offshore. In November, the salty open lake

body also hosts tens of thousands of common goldeneye,

green-winged teal, and northern shovelers which appear to

be foraging on brine shrimp and their eggs. Research is

being initiated by the Utah Division of Wildlife Resources

(DWR) to validate the role of cysts in winter waterfowl diets.

Waterfowl can make use of the salt water areas due to the

presence of salt glands which facilitate nasal excretion of

excess salts ingested in water and food. 

Numerically, ducks represent the lion’s share of migrating waterfowl, but GSL also serves as a major staging area

for tundra swans and Canada geese (figure 3). Approximately 75 percent of the western population of tundra swans

migrates along an interior route from their Alaska breeding

areas through GSL, eventually reaching their wintering areas

in the central valley of California. Swans stage for a substantial time in marshes of GSL before moving on. Peak fall

populations of 40,000 to 60,000 swans regularly occur. Tundra swans loaf in shallow mud flats in the sanctuary of the

BRMBR and mainly feed on sago pond weed tubers, which

are found primarily in the deep, persistent fresh-water

impoundments of GSL. Prior to the GSL flooding in the

1980s, swan use was distributed over much of the east shore,

but currently is focused on the BRMBR. Little swan use of

salt water areas occurs on GSL. Although wintering tundra

swans feed heavily in agricultural environments in California, their use of fields around GSL during migration has only

rarely been documented (Nagel, 1965). Trumpeter swans

(Cygnus buccinator) also use GSL during migration, but

information on timing and abundance is scarce and inconsistent. Trumpeter swans appear to prefer small, more vegetated wetland complexes.

Most Canada geese migrating through Utah are part of

the Rocky Mountain Population (RMP) which breeds

throughout the intermountain west and largely winters in

Idaho, Utah, and the lower Colorado River region of Arizona

and southern California. In recent years, smaller races of

Figure 2. Monthly duck populations on the Great Salt Lake as measured by ground surveys on state and federal management areas (averaged for years 1993-1998).

Figure 3. Monthly Tundra swan and Canada goose populations on the

Great Salt Lake (averaged for years 1993-1998).
Canada geese, likely from interior Alaska and Canada, have

become more prevalent during the fall migration, but remain

a small proportion of all geese passing through. Based on

midwinter surveys, it is likely that about 35,000 (30 percent

of the population) RMP geese migrate through GSL annually. Lesser snow geese (Anser c. caerulescens), and Ross’

geese (Anser rossii) historically frequented GSL in spring

and fall, but recently their use has been restricted mostly to

the spring period. Much conjecture exists regarding the loss

of fall use by lesser snow geese, but reasons remain unclear.

Theories include disturbance from increased aircraft use

(particularly from helicopter use in the 1960s at Hill Air

Force Base), habitat changes, and short-stopping of geese on

large reservoirs in southern Canada.

The value of high-quality habitat in key migration areas,

such as GSL, is important for several reasons. Flight is energetically demanding and many waterfowl travel thousands of

miles between breeding and wintering areas. Consequently,

waterfowl need periodic stops to replenish energy and water

reserves used in migration. Also, most waterfowl need to

carry reserves necessary for egg development to their nesting

areas. Good-quality habitat along migration routes is therefore important for enhancing successful migration and reproduction. GSL marshes are expansive and diverse, have large

areas of open water, and are rich in a variety of invertebrate

and plant food resources. These features are the keystone of

GSL’s value to migrating waterfowl. The evolution of waterfowl migrations through GSL is likely related to its historic

importance in providing high-quality habitat during fall and

spring migration periods.

Waterfowl Breeding and Production

Although 13 species of ducks potentially breed in GSL,

seven are common nesters. Ducks generally select emergent

or upland cover for nest construction and remain secretive

during the nesting period. For these reasons, duck populations can be difficult to inventory and estimate. Standardized, aerial, breeding bird transects conducted by DWR from

1956-98 within the GSL region, indicated an average of 75

ducks per square mile of habitat, but range from 24 to 276

ducks per square mile (2.59 km2) among these years (figure

4). Using 1995-98 data (corrected for visibility bias by

species), and a habitat base of 404,694 acres (163,779 ha2)

(Jensen, 1974, 1st and 2nd magnitude marsh), the estimated

total breeding duck population of the lake exceeds 230,000

in an average year (table 4). These densities of breeding

ducks compare favorably with the highest known duck densities on broad landscapes in North America. For cinnamon

teal, redheads, and gadwall, GSL is nationally recognized as

a key breeding area.

Production of ducks is also difficult to estimate for GSL

due to the secrecy of hens with young broods. No surveys

are currently conducted to try to estimate lake-wide production. However, crude estimates of production can be made.

Using an average clutch size of eight eggs, and assuming

there are 115,000 breeding pairs of ducks (table 4), the potential annual duck production from GSL could equal 920,000

ducklings. The realized production is undoubtedly lower due

to nest and brood predation, and other factors that limit

reproductive success. Recent studies of duck nesting success

at the Salt Creek, Public Shooting Grounds, and Harold

Crane WMAs from 1988-92, indicate nest success rates vary

from 2 percent to 59 percent. Avian and mammalian predation is believed to be the major causes of nest failure (Huener and Manes, 1992a, b). No studies of brood survival have

been conducted recently in GSL marshes, but the substantial

predation of duck nests would suggest broods are also heavily impacted. Using a 20 percent nest success rate for each

hen, and a 50 percent brood loss rate reduces the estimated

GSL production to about 92,000 fledged ducks. A second

method to estimate lake-wide duck production would be to

use nest densities from these same studies (rather than using

aerial breeding bird densities), and apply the same hen and

brood success rates. Using an average nest density of 0.20

nests/acre (DWR studies indicate a range from 0.04 to 1.29

nests/acre), a habitat base of 404,694 acres (163,779 ha2), the

same clutch size, and hen and brood success rates as above,

yields a production estimate of about 81,000 fledged ducklings. Sanderson (1980) reports that production from the

Bear River and Weber River marshes alone exceeds 100,000

fledglings annually, but does not say how this estimate was

generated. Although these estimates are overly simplistic

and apply parameter estimates from small study areas to the

entire GSL system, they nevertheless are useful in demonstrating the potential and realized production from GSL.

Great Salt Lake - An Overview of Change 351

Figure 4. Densities of ducks counted during May aerial surveys on the

Great Salt lake by the Utah Division of Wildlife Resources.

Table 4. Estimated breeding ducks on the Great Salt Lake based on aerial transects conducted by the utah Division of

Wildlife Resources, 1995-98. (unpublished data, DWR files).

Birds Indicated Visibility Expansion GSL

Breeding Correction Factor Estimated

Birds Breeding

Birds

Mallard 131 11 32 48,099 

Pintail 33 9 32 9,436 

Shoveler 128 6 32 26,510 

Gadwall 343 5 32 59,944 

C Teal 97 13 32 40,702 

Redhead 214 4 32 29,642 

Canvasback 3 4 32 347 

Ruddy 302 2 32 16,389 

Total 231,068

Note:

Indicated breeding birds determined from aerial transects

Visibility correction based on DWR studies in the 1980s

Expansion factor = Acres of 1st and 2nd magnitude marsh /aerial

transect acreage
The timing of nest initiation and hatching periods for

ducks in GSL is influenced by weather, but some patterns

persist year to year. Mallards and pintail are the first ducks

to initiate nesting, with mean initiation dates during the first

two weeks in May. Shovelers, cinnamon teal, and redheads

follow in late May, with gadwall the last to nest. Nest initiation, however, has been observed as early as the end of

March, and as late as the beginning of July in some years.

The incubation period for ducks ranges from 20-30 days, so

hatching dates follow initiation dates by about a month.

GSL is also a major breeding area for Canada geese

(table 5). Lake-wide surveys conducted annually by the

DWR from 1980 to 1998 indicate that an average of 438

pairs of geese produced about 1,663 young each year. These

figures represent 60 percent of the breeding geese in Utah

and 53 percent of the statewide production of young.

Because we likely do not see all pairs or young during survey flights, these estimates represent minimum numbers.

Geese are the earliest nesting waterfowl species in Utah, with

most nests initiated in March and April.

The role of endogenous nutrient reserves and food

resources on waterfowl reproduction is well documented

(Ankney and MacInnes, 1978; Krapu, 1979; Owen and Reinecke, 1979; Raveling, 1979; Ankney and Afton, 1988).

Ducks and geese rely heavily on lipid reserves acquired in

winter and spring, which are carried to breeding areas for egg

production. Much of the protein required for eggs, however,

comes from food resources in the breeding areas. Food

acquired during incubation recesses is also believed to be

important for successful reproduction, particularly in ducks,

although most energy for incubation comes from fat reserves.

After hatch, growth of young birds, as well as recovery of

body condition in females, is dependent on high-quality

foods. Abundance and availability of invertebrates are particularly important during these reproductive periods. Wetlands of GSL offer a diversity of food-producing plants and

associated invertebrate communities to fuel the energetic

needs of reproduction for thousands of locally breeding

waterfowl, and millions of migrating waterfowl that breed

farther north.

Waterfowl Molting

All birds molt to replace damaged and worn feathers.

Among waterfowl, there are numerous differences in the timing and extent of the molting process, and these differences

in molt patterns are used, in part, to taxonomically group

waterfowl species. Generally, geese and swans molt once

annually, whereas ducks go through at least two partial molts

each year. A unique characteristic of waterfowl, not shared

with many other bird groups, is a complete, simultaneous

wing molt that leaves individuals flightless for three to five

weeks during summer. In geese, breeding-age adults molt

while raising their young, often forming aggregations of

mixed flightless families called “creches.” Non-breeding

geese (one and most two year olds) and failed breeders commonly depart the breeding areas all together and form large

“molt migrations” to areas farther north where they are relatively free from predators. Leaving the breeding areas to

molt in higher latitudes is also believed to reduce competition for food with successful breeders and their young, as

well as to provide molting geese more available time to forage due to increased day lengths. Male ducks show similar

patterns by molting wing feathers soon after the breeding

period. Some species form large flocks and migrate to traditional areas before molting. Female ducks generally molt

after their broods fledge in local breeding areas.

Replacing feathers requires nutrients above the normal

basic metabolic needs. The complete wing molt is particularly taxing on protein resources due to the need for replac352 Utah Geological Survey

Table 5. Breeding pairs and production of Rocky Mountain Population of Canada geese in Utah (from unpublished UDWR data files).

GSL UTAH GSL as % of Utah

Year Breeding Pairs Production Breeding Pairs Production Breeding Pairs Production

1980 446 2,025 654 2,926 68.2% 69.2%

1981 382 1,754 674 3,122 56.7% 56.2%

1982 597 2,802 789 3,740 75.7% 74.9%

1983 412 1,974 581 2,733 70.9% 72.2%

1984 139 629 289 1,343 48.1% 46.8%

1985 153 715 369 1,564 41.5% 45.7%

1986 238 1,033 458 2,172 52.0% 47.6%

1987 294 1,024 590 2,428 49.8% 42.2%

1988 283 920 601 2,279 47.1% 40.4%

1989 263 791 651 2,827 40.4% 28.0%

1990 644 1,479 912 2,866 70.6% 51.6%

1991 378 1,317 681 2,633 55.5% 50.0%

1992 738 1,844 1,030 3,430 71.7% 53.8%

1993 927 1,552 1,225 3,014 75.7% 51.5%

1994 552 2,992 889 5,137 62.1% 58.2%

1995 354 1,931 741 4,355 47.8% 44.3%

1996 524 2,442 991 5,106 52.9% 47.8%

1997 414 1,890 743 3,656 55.7% 51.7%

1998 582 2,487 947 4,677 61.5% 53.2%

Average 438 1,663 727 3,158 60.2% 52.7%
Great Salt Lake - An Overview of Change 353

ing all wing feathers in as short of a period as possible. Most

waterfowl species rely, in part, on stored lipid reserves to fuel

the energetic costs during molt, but rely heavily on protein

from food resources for nutrient requirements of feather

development. 

Geese generally prefer large, open, water bodies to molt,

whereas ducks take advantage of both open water and dense

emergent marshes. Both strategies are believed to be mechanisms to avoid predators during the flightless period. Molting areas are also generally rich in food resources because

the high nutrient demands of feather development coincide

with a time when mobility and access to food is limited by

the inability to fly. Availability of invertebrates as a protein

source is a particularly important feature of high-quality

molting environments. 

GSL is host to substantial numbers of molting waterfowl, including both local breeding birds, and large numbers

of molt migrants. Tundra swans do not molt in Utah because

they are not present during the summer molting period.

The RMP Canada geese, including some from Utah,

migrate north to other intermountain states and to Canada to

molt during summer (Krohn and Bizeau, 1979; Krohn and

Bizeau, 1980). Some are believed to travel as far north as the

Northwest Territories in Canada. Utah has three, recognized,

major molting areas for Canada geese that are important for

local geese, as well as migrants from other states. Two of

these areas are located on GSL (table 6). Bear River Bay,

along the east side of Promontory, is the largest molting area

in Utah, with over 7,000 geese recorded during the June survey in recent years. This area represents one of the largest

concentrations of RMP Canada geese molting in the Rocky

Mountain region and its attractiveness is likely related to the

lack of disturbance and sheer size of this open body of water.

Bear River Refuge also receives substantial use from molting

geese, although use in recent years has declined and possibly

shifted to the Promontory region.

Pintail and green-winged teal are the most common

ducks molting within GSL. Molt migrants begin arriving in

mid-June, with most completing the wing molt in July and

early August. Unlike geese, most of the molting teal and pintail in GSL are males arriving from northern breeding areas.

Although large concentrations of molting pintail and greenwinged teal occur on the marshes of the Bear River delta,

these ducks can be found molting throughout the fresh-water

marshes of GSL. Local breeding ducks begin the wing molt

in July, while late-nesting species, such as redheads and

ruddy ducks (Oxyura jamaicensis rubida) can still be found

flightless in September.

Wintering Waterfowl

Waterfowl have relatively large and compact body forms

compared to many bird groups. They also feature thick

feathers and an abundant down layer. These characteristics

afford them the thermal capacity to winter in higher latitudes

and colder climates than many other waterbirds. Because

migration is energetically expensive and often risky, waterfowl tend to winter as far north as they can to find adequate

food and open water. Availability of open water and food are

consequently the limiting factors controlling the distribution

and abundance of waterfowl in winter. 

The fresh-water marshes of GSL normally freeze by the

first week in December, eliminating access to most aquatic

food sources important to waterfowl. Major movements of

waterfowl to other wintering areas accelerates during this

ice-up period and populations on GSL reach their annual low

by January. Although GSL holds the majority of waterfowl

in the state during winter, populations represent only 2 to 8

percent of ducks, geese, and swans wintering in the Pacific

flyway (table 7). The Pacific flyway is a waterfowl migraTable 6. Use of major molting area by the Rocky Mountain Population of Canada geese in the Intemountain West. 

(from unpublished UDWR data files).

Wyoming Montana Utah

Year Wheatland Res. Yellowstone Lk. Jackson Lk. Lima Res. Neponset Res. Promontory Bear River Refuge

1980 8,500 3,500 10,000 1,716 4,156 1,954 

1981 7,500 3,000 3,000 2,293 3,823 2,429 

1982 5,000 7,275 4,800 2,275 3,929 2,903 

1983 5,000 7,470 5,500 1,312 5,934 636 

1984 4,500 7,685 780 9,000 1,750 7,212 3,394 

1985 6,500 7,298 300 528 1,642 1,712 

1986 7,000 2,810 900 10,958 935 3,885 1,723 

1987 6,815 6,860 750 10,300 628 2,738 2,549 

1988 8,965 6,900 1,500 565 3,101 1,202 

1989 9,250 5,035 1,380 771 3,017 3,134 

1990 7,563 3,955 225 

1991 7,420 1,990 220 626 2,911 1,312 

1992 6,210 1,539 866 3,373 1,215 

1993 9,430 1,907 653 991 4,155 78 

1994 10,600 1,055 474 1,455 3,587 16 

1995 878 7,136 1,418 

1996 6,574 2,929 435 739 7,016 109 

1997 982 7,252 267 

1998 994 11,893 110 

Average 7,302 4,451 692 7,651 1,128 4,820 1,453 
354 Utah Geological Survey

tion route located within the Intermountain West and Pacific

coast states.

Some species of waterfowl can, however, switch to alternative habitats and food resources, and remain in the GSL

area in significant numbers during winter. Canada geese and

mallards exploit waste grains in adjacent agricultural areas as

long as they remain snow-free. Mallards and pintail utilize

riverine habitats and impoundment discharge areas where

flowing fresh water remains open and food persists. An apparently unique food resource on GSL, utilized by large

numbers of green-winged teal, shovelers, and goldeneye, are

brine shrimp cysts found in the salt-water areas of the south

arm which remain open long after the fresh-water areas

freeze. Flocks of ducks are seen regularly feeding within

wind-generated egg masses concentrated on the lake surface,

along ice edges, and against shorelines. Some debate exists

regarding the food value of cysts to water birds, but MacDonald (1980) reported assimilation efficiencies of 20 to 35

percent for shelducks and flamingos experimentally fed

cysts. Research by DWR to determine the value of cysts in

the diets of waterfowl on GSL is underway. Shovelers and

green-winged teal appear to still require fresh water based on

their heavy use of salt-water habitats that are in close proximity to fresh-water sources. Two particularly important

areas where these resources occur is the area from Saltair to

the south shore of Antelope Island, and the off-shore area

between the Ogden Bay WMA and Fremont Island. 

Shorebirds

There are 47 species of shorebirds which breed, or winter, in the Pacific flyway, of which 28 are relatively rare, or

utilize non-wetland habitats (Page and others,1992). Twenty-three of the 47 species occur with reasonable regularity

within the GSL ecosystem. Of these 23, 13 species breed in

the arctic or sub-arctic. The other 10 species breed on the

prairies, or in the intermountain west. In addition to these 23

species which occur regularly, 11 other species have been

recorded on rare occasions on GSL (Paton and others, 1992)

(table 8).

By examining records from the U.S Fish and Wildlife

Service (USFWS), and various issues of American Birds,

Skagen and Knopf (1990) suggest that the Intermountain

West is frequented more often by species of large shorebirds

during migration, for example, the American avocet, blacknecked stilt (Himantopus mexicanus), and marbled godwit

(Limosa fedoa), than by small species of neotropical migrant

shorebirds. A preponderance of peeps (small sandpipers)

move across the Great Plains. These authors also discovered

a general pattern among shorebird migration pathways

through the continental United States. The distance that individual species migrated also provided a key to shorebird size.

In spring, the intermountain area hosts primarily short-distance migrants whose breeding range extends south of 60

degrees north latitude. These are usually large shorebird

species. By contrast, long-distance migrants and species that

breed north of 80 degrees north latitude pass through the

Central Plains. These are most often smaller species. In fall,

migratory species that winter in the contiguous 48 states have

greater representation in the intermountain region. Species

that winter south of the equator have greater representation

as migrants through the plains. These findings were substantiated for the GSL ecosystem through several survey

efforts and observations in recent years (Halpin and Paul,

1989; Fellows and Edwards, 1991; Page and others, 1992;

Paton and others, 1992, Shuford and others, 1995; Paul,

unpublished data).

Shorebird Surveys

In 1988, a Pacific flyway project was initiated by Point

Reyes Bird Observatory, cooperating agencies, and non-profit organizations. The scope of the project included all coastal

and interior wetlands within the Pacific flyway west of the

Rocky Mountains, from Alaska through Baja, California and

along the west coast of northern Mexico. The project methods were designed to survey the wetlands suspected to possess high species richness or high numbers of individuals.

Surveys were coordinated to canvass these areas in a one- or

two-day intensive effort, using a large, organized group of

experienced birders. In Utah, the GSL ecosystem was the

primary focus area. From 1988 to 1993, the surveys were

mostly accomplished by ground crews. During the 1994 and

1995 seasons, more comprehensive aerial and ground surveys of this area were achieved. The DWR and USFWS

were principle organizers in these two years. On August 10

and 11, 1994, 436,000 shorebirds of 21 species were recorded within the GSL ecosystem. Noteworthy, there were

252,000 American avocets, 65,000 black-necked stilts,

32,000 long-billed dowitchers (Limnodromus scolopaceus),

and 16,000 marbled godwits. The numbers of avocets and

stilts on GSL proved to be many times larger than those

reported from any other wetland in the Pacific flyway. The

comparative data also bore out that GSL is the only major

staging site for marbled godwits in the interior of North

America. The 1995 survey included a spring survey on April

25 that accounted for 68,000 shorebirds consisting of 17

Table 7. Great Salt Lake mid-winter waterfowl populations relative to Utah and Pacific Flyway populations, 1994-98 (from unpublished

UDWR data files).

1994-98 MID-WINTER AVERAGE GSL as % of

Species Group GSL UTAH PACIFIC FLYWAY Utah Flyway

Ducks 104,821 151,778 4,688,383 70.2% 2.3%

RMP Canada Geese 3,876 13,378 98,007 31.0% 4.2%

Swans 7,028 7,140 91,003 98.4% 7.7%
Great Salt Lake - An Overview of Change 355

species. It is well known that spring shorebirds returning

north to their breeding grounds move through, and into, the

United States in a more progressive pattern than in the fall.

In the fall, shorebirds will stage in one place for several days,

or even weeks, in order to add body fat for fuel for a marathon flight south. (staging is when time is spent in molt and

foraging to prepare for a continued migration along a migratory path). The fall 1995 survey was conducted on August

18, a week later than in 1994. The survey accounted for

340,000 shorebirds comprised of 18 species. The most numerous species were American avocets, Wilson’s phalaropes,

black-necked stilts, long-billed dowitchers, and western

sandpipers (Calidris mauri) (table 9), but counts were slightly lower than in 1994. The smaller number of shorebirds

counted in the fall of 1995 could be due to missing the peak

migration of early August.

Table 8. Shorebirds of the Great Salt Lake (Paton and others, 1992).

Arctic/Subarctic Prairie/Intermountain Rare Visitors/Number

Breeders Breeders* of GSL Records

Black-bellied plover Snowy plover Lesser golden plover/28

Semipalmated plover Killdeer Mountain plover/1

Greater yellowlegs Black-necked stilt Solitary sandpiper/19

Lesser yellow legs American avocet Hudsonian godwit/1

Whimbrel Willet Semipalmated sandpiper/15

Red Knot Long-billed curlew Pectoral sandpiper/26

Sanderling Marbled godwit* Dunlin/59

Western sandpiper Spotted sandpiper Curlew sandpiper/1

Least sandpiper Common snipe Buff-breasted sandpiper/1

Baird's sandpiper Wilson's phalarope Short-billed dowitcher/1

Stilt sandpiper Red phalarope/6

Long-billed dowitcher

Red-necked phalarope

*All breed on GSL unless indicated by *

The Great Salt Lake’s low-gradient bottom provides extensive shallow

water covered flats for Western Sandpipers, and other shorebirds, to

forage for brine flies and other invertebrates.

Wetlands provide habitat for these Long-billed Dowitchers and many

other water birds. These wetlands, when associated with Great Salt

Lake, provide a unique habitat relationship that supports millions of

water birds.

Table 9. Numbers of shorebirds recorded during surveys of

wetlands at the Great Salt Lake, Utah. Surveys occurred on

August 10 and 11 in 1994 and on August 18 in 1985. (Point

Reyes Bird Observatory, 1995)

Species 1994 1995

Black-bellied plover 15 40

Snowy plover 384 58

Semipalmated plover 2 2

Killdeer 198 133

Black-necked stilt 65,446 41,470

American avocet 251,880 188,186

Stilt/Avocet 600 0

Greater yellowlegs 91 3+

Lesser yellowlegs 151 5+

Yellowlegs spp. 177 215

Solitary sandpiper 3 0

Willet 152 35+

Spotted sandpiper 37 7

Long-billed curlew 2 8+

Marbled godwit 16,315 10,979

Western sandpiper 330 714+

Least sandpiper 3 10

Semipalmated sandpiper 2 5

Baird's sandpiper 21 27

Peep sandpiper spp. 1,930 20,723

Dowitcher spp. 31,940 28,125

Wilson's phalarope 748 13,692+

Red-necked phalarope 119 0

Phalarope spp. 65,195 35,725

Shorebird spp. 69 0

Total 435,810 340,162
356 Utah Geological Survey

The BRMBR possesses the largest maintained database

that includes shorebird numbers for a portion of the ecosystem. They have records spanning several decades; compiled

data is complete from 1948 to 1965 and from 1990 to present (V. Roy, personal communication).

There is a (DWR) database for Wilson’s phalaropes and

red-necked phalaropes (Phalaropus lobatus) from 1982 to

present with the exception of three years. Studies were conducted in cooperation with Hubbs Seaworld Research Institute in San Diego, a principal investigator of Mono Lake,

California and its avian resources. Mono Lake, a significant

salt lake on the west side of the Great Basin, and GSL are

important locations for phalaropes and other birds associated

with salt-driven environments of the Great Basin. The studies of phalaropes at GSL demonstrate that the lake is the most

important stopover site in the world for these two species. In

a single day, there may be in excess of one-half million Wilson’s phalaropes and more than one-quarter million rednecked phalaropes. Wilson’s phalarope numbers typically

peak in late July. This is relatively early compared with other

shorebirds during their southerly migration. The Pacific flyway project did not detect large phalarope numbers.

Several studies of shorebirds, many of them thesis and

dissertation work from graduate school research projects,

have provided information regarding population biology,

habitat selection, diets, seasonal occurrence, and ecological

relationships. In addition, significant findings have been

recorded in field notes of researchers as an ancillary addendum to their specific research projects. Paton and Edwards

(unpublished data), have compiled extensive field notes on

shorebirds from 1990 through 1993. Their study of the ecology of snowy plovers (Charadrius alexandrinus) on GSL

estimated a population of 10,000 individuals for 1992, the

largest concentration of snowy plovers in North America and

possibly the world (Paton and Edwards, 1992; Paton, 1997).

In 1997, Paton returned to GSL with a field crew and conducted an intensive population census. He concluded that

there was no significant difference in snowy plover abundance between the early 1990s and in 1997 (Paton,1997).

Coastal populations of snowy plovers are in decline and listed as threatened under the Endangered Species Act, making

the protection of the large interior population of GSL acutely important.

During 1990 and 1991, Suzanne Fellows carried out

graduate research on the temporal and spatial distribution of

GSL shorebirds along maintained travel routes, mostly within associated wetlands found on the northeast and northern

parts of the lake. Certain methods used in Fellows’ study

proved to be quite useful for censuses of wildlife management areas with established roads and dikes. This work provided the basis for a more comprehensive waterbird survey

in 1997 (Fellows and Edwards, unpublished report). Until

1997, no such appraisal of shorebirds and other waterbirds

had been conducted at GSL.

In 1996, plans were developed to establish an ecosystem-based waterbird survey by biologists associated with

avian management and research within the Great Salt Lake

area. Several different survey protocol types were used in

order to conduct a census of all habitats, that is shoreline,

wetland, and open water. This community-based effort

sought to plot the estimated numbers of individual species

populations during breeding season and migration, their periods of use, location and habitat characteristics of use areas

against GSL elevations over a five-year period. Survey

methods included total counts, area counts, point samples,

and aerial counts. This waterbird survey was conducted by a

cadre of 85 surveyors representing multiple agencies, nonprofit organizations, and interested publics. The survey area

covered 44 sites encompassing the wetlands, shores and

open-water areas of the south, east and north portions of

GSL. As close as possible, surveys were conducted every

tenth day, with a designated or “preferred” day on which the

survey should be completed. Seventeen surveys were conducted each year except for 1997, producing a five-year

mean for the peak survey period (August 24 to September 2)

of 1,104,946 water birds. From these counts bird-use days

were calculated at 86,000,000 for 1997-1999. This number

reflects the estimated number of birds present and their duration of stay at GSL. Over the five-year study period GSL elevation fluctuated in excess of 4.5 feet. The relatively large

difference between lake elevations brought about a significant difference in overall numbers of birds and species between years. At some individual survey sites, there were also

significant differences observed in species composition, as

well as in species numbers. The changes noted in species

composition and numbers is considered an artifact of the profound change in habitat types driven, by the highly transiRibbons of Wilson’s phalaropes rise from the Layton Wetlands Preserve

and nearby state lands. These concentrations of hundreds of thousands of individuals were a common sight during the years immediately following the 1980s high-lake years. They foraged on copious numbers of brine flies that in turn fed on the detritus left behind as the lake

receded from decaying stands of wetland emergent vegetation.

Closeup of flocking Wilson’s phalaropes.
Great Salt Lake - An Overview of Change 357

tory shoreline during lake fluctuations. The waterbird survey

data continue to confirm the importance of GSL for breeding

and migratory shorebirds, colonial nesting birds, and other

waterbirds.

Some Noteworthy Shorebirds of the Great Salt Lake

The ecosystem diversity, magnitude, and setting of

GSL’s ecosystem help support an astounding variety and

abundance of shorebird species (table 8). Five species stand

out as important examples of the ecosystem resources, especially when regarding the relationship between salt and

freshwater environments. The red-necked phalarope, Wilson’s phalarope, American avocet, black-necked stilt, and the

snowy plover are these species.

Wilson’s and Red-necked phalaropes

Of the three species of phalaropes in the world, two

occur on GSL in considerable numbers and represent a substantial proportion of the world’s population. The Wilson’s

phalarope population on GSL in July frequently represents

more than a third of the world’s population (figure 6). The

magnitude of the Wilson’s phalarope staging population was

the main factor in the designation of GSL as a hemispheric

site within the Western Hemisphere’s Shorebird Reserve

Network, currently one of six sites in the United States. To

qualify as a site of hemispheric importance, the area in question must host at least 500,000 shorebirds or 30 percent of a

flyway population. GSL met both criteria for just the Wilson’s phalarope.

The Wilson’s phalarope breeds from the prairie potholes

to the Intermountain West. Outside of its breeding season, it

is a salt lake specialist where it exploits halophiles as a food

resource during the respective warm seasons of North and

South American summers. This species is often polyandrous

with reversed sex and parenting roles. The female defends a

territory, courts males, breeds, lays eggs for the male to incubate and brood, and, under ideal conditions, does the same

with other males in the same nesting season. At GSL,

females are the first to arrive in June after breeding and leaving the males to care for the nest and young. On July 3,

1982, a flock of 118,000 Wilson’s phalaropes were 95 to 98

percent females. During the early weeks of staging, Wilson’s

phalaropes are often associated in same sex flocks. Males

filter in during July, and by the end of the month this species

reaches peak numbers at GSL (table 10). The timing, forage

conditions, and behavior of the Wilson’s phalarope at GSL is

similiar to Wilson’s phalarope activity at Mono Lake, California (Jehl, 1988).

During their stay at GSL, Wilson’s phalaropes spend

their time eating, and molting into post-breeding plumage.

Eating takes the form of hyperphagia. It was estimated that

these birds put on two grams of body weight per day during

their stage at Mono Lake (Colwell and Jehl, 1994). Small

samples suggest that these weight gains occur at GSL as well

(DWR, unpublished data). By the end of their stage at GSL

and Mono Lake, the birds have nearly doubled their body

mass, with the additional weight stored as fat. They need the

fat reserves gained at staging sites for the substantial flight to

the South American wintering grounds. By mid-August,

most Wilson’s phalaropes have departed for the saline lakes

of Bolivia, central Argentina, and other suitable saline environments. In North America in the spring, they return to

GSL around late-April and May on their way to their breeding grounds. At GSL and saline lakes of South America, they

forage on the same halophile groups (brine shrimp and brine

fly), but different species. GSL brine flies and brine shrimp

achieve their greatest abundance during the nesting and

migration periods of the Wilson’s phalarope and many other

shorebirds (Collins, 1980; Stephens, 1997).

Table 10. Results of annual surveys of Wilson's phalaropes conducted during peak staging period on the Great Salt Lake, Utah (1982-1998),

some years not surveyed.

Lake Survey

Year Date Elevation (ft.) Number Method

1982 Jul 27 4200.25 403,770 Aerial

1984 Jul 12 4208.80 54,000 Aerial

1986 Jul 25 4210.90 387,157 Aerial

1987 Jul 27 4210.45 193,770 Aerial

1988 Jul 29 4207.80 56,215 Aerial

1989 Jul 27 4205.15 85,850 Aerial

1990 Jul 26 4203.15 579,132 Aerial

1991 Jul 26 4201.90 603,333 Aerial

1992 Jul 31 4200.40 115,600 Aerial

Jul 31 200,000 Boat

1993 Aug 5 4200.95 229,000 Aerial

1994 Jul 29 4199.30 110-125,000 Aerial

1995 Jul 29 4200.15 267,000 Aerial

1996 Jul 31 4199.90 250-300,000 Aerial, Boat & Land

1997 Jul 30 4200.70 191,733 Aerial

1998 Jul 29 4203.10 262,636 Aerial
358 Utah Geological Survey

Wilson’s phalaropes are especially in need of a readily

accessible, easily taken, and abundant protein source from

June through mid-August. At saline lakes, brine flies and

brine shrimp are foraged at different intensities by the different sexes of the Wilson’s phalarope (Jehl, 1988). The vast

south arm of GSL, with its extensive open water and shallow

shorelines, provides the primary foraging habitats of Wilson’s phalaropes during the critical period prior to their long

migration. This part of the lake supports a robust population

of brine shrimp and brine flies. On these shores, the brine fly

population is estimated to be at 370 million adult flies per

linear beach mile (Oldroyd, 1964). Farmington Bay, Fremont Bay, and Bear River Bay are also used by staging

phalaropes. During the flood years of the 1980s, the north

arm of the lake was the key habitat for both Wilson’s and rednecked phalaropes, however, the numbers of individuals

were fewer at GSL than previous years, and for some years

that followed in the 1990s (Paul, unpublished data).

Red-necked phalaropes arrive at GSL from their sub-arctic breeding grounds later than Wilson’s phalaropes, and they

linger on into September. Red-necked phalarope biology is

similar to that of the Wilson’s phalarope with regard to

reversed sex roles. Red-necked phalaropes often use different parts of GSL than the Wilson’s. The bay west of Stansbury Island (before the development of the salt extraction

industry ponds), Carrington Bay, the lake area around Hat

Island, and the open water west of Antelope Island (figure 1)

have been preferred habitats of the red-necked phalarope in

the past.

In general, red-necked phalaropes seem to be more

pelagic than Wilson’s phalarope while at GSL. The distribution of Wilson’s and red-necked phalaropes within the GSL

ecosystem is a fitting example of how lake dynamics affect

the distribution and abundance of avian food resources, thus

in turn, affecting the distribution of birds, like phalaropes,

whose principle mission is to locate plentiful and accessible

nourishment. The red-necked phalarope diet seems to consist largely of adult brine flies (table 11) (Paul and Jehl,

unpublished data). The two phalarope species are the only

two shorebirds to utilize open, deeper lake water and its

resources. After leaving GSL, red-necked phalaropes spend

the winter offshore in open seas of the Pacific Ocean.

American Avocets and Black-necked Stilts

Of the seven species of avocets and stilts in the world, all

are associated with saline or alkaline lakes at some point in

their life history. American avocet and black-necked stilt

populations are intrinsically tied to western North America,

and are found in the greatest numbers in salt-rich terminal

lake systems and saltwater estuaries. The largest populations

are located in the Great Basin, with the highest number of

individuals occurring at GSL. Here, a single-day count of

American avocets and black-necked stilts have exceeded

250,000 and 65,000, respectively. These numbers are larger

than those reported from any other wetland in the Pacific flyway (Shuford and others, 1995).

GSL provides both breeding and migratory habitats for

avocets and stilts. Starting in March, American avocets

begin their arrival on the lake. They have just come from

their wintering grounds, mostly from coastal areas in California, Texas, and western Mexico - for example, Marismas

Nacionales in Nayarit (Morrison and others, 1994; Shuford

and others, 1998; M. Cervantes, Wetlands International coordinator for Mexico, personal communication, 1998). For

some avocets, nesting begins in early April, but may occur as

late as July. They are ground nesters, often forming loose

colonies. Nests are positioned in relatively open terrain and

typically are comprised of vegetation and other debris, or

simply occur in a shallow depression. These nest sites are

often near or surrounded by water. The mean clutch size is

four eggs. Hatching rates are not well understood on GSL,

but can range from 43 to 90 percent nest success in neighboring states (Gibson, 1971; Sidle and Arnold, 1982; Dole

1986). Avocet nesting on GSL is often concurrent with that

of black-necked stilts. An estimate of 52,000 to 53,000

Table 11. Percentages of adult, pupae and larvae brine flies in stomach contents of red-necked phalaropes from the Great Salt Lake, Utah,

1992. Diets of all red-necked phalaropes sampled comprised completely of the brine fly species (Paul and Jehl, unpublished data).

Weight, grams

Date (sex/age) Percentages

July 31 37.1 (F/Ad) 100% pupae

August 10 38.1 (M/Ad) 100% adult

35.3 (F/Ad) 95% adult, 5% pupae

34.5 (M/Ad) 95% adult, 5% pupae

August 27 30.0 (M/Ad) larvae, pupae-well digested

37.2 (F/Ad) larvae, pupae-well digested

37.9 (M/Juv) larvae, pupae-well digested

34.5 (?/Juv) larvae, pupae-well digested

43.8 (F/Ad) 95% larvae, 5% pupae

41.3 (F/Ad) 100% larvae

44.2 (F/Juv) 95% pupae, 5% larvae

38.9 (?/Juv) 60% larvae, 40% pupae

33.1 (M/Ad) 100% larvae

October 5 42.8 (M/Ad) 70% pupae, 30% larvae

36.6 (M/Ad) 90% pupae, 10% larvae

49.2 (F/Ad) 100% pupae
Great Salt Lake - An Overview of Change 359

breeding American avocets was ascertained from the 1997-

98 GSL Ecosystem Waterbird Survey Project (Paul and others, 1998b).

GSL breeding avocets utilize various species of Chironomidae, including brine flies in all life stages, and Corixid nymphs and adults. However, Chironomidae larvae often

provide 63 to 79 percent of their diet (Osmundson,1990).

During late summer and early fall, staging avocets assemble

in massive flocks along the shores of GSL. These flocks

often number in the tens of thousands, and often occur in

association with large numbers of Franklin’s gulls, California

gulls, and black-necked stilts (Paul, unpublished data).

These aggregations of avocets and other waterbirds are most frequently found feeding upon

dense populations of brine flies. These foraging areas are situated in open water with depths

around 3-9 inches (7.5-23 cm) deep. The avocet is a consummate example of the rich bird

life that utilizes the shallow, warm, food-rich,

and low-gradient shorelines of GSL. Avocets,

like many shorebird species, follow the shoreline as it fluctuates through, and between, the

seasons. During high lake periods, as during

1984 through 1987, shoreline foraging and

nest habitats are significantly impacted.

In 1997 and 1998, the American avocet

was chosen as the avian ambassador for the

Linking Communities, Wetlands, and Migratory Birds Project. This project was initiated by

Wetlands for the Americas of Ottawa, Canada,

and by the Western Hemispheric Shorebird

Reserve Network of the Manomet Center for

Conservation Science in Manomet, Massachusetts, USA. The project is an effort to strengthen local and international community involvement surrounding wetlands’ biological, social,

cultural, and economic values. GSL was chosen as the site to represent the project for the

United States. Chaplin and Quill Lakes, located in Saskatchewan, Canada, and Marismas

Nacionales, Mexico, were the sites selected to

represent the other two countries involved.

The American avocet was chosen because of its notable relationship with all these areas, its extensive breeding population in the prairies of southwestern Canada, its breeding and

significant staging population at GSL, and its large wintering

population at Marismas Nacionales. The avocet connects

these sites through its flight and life history, just as the project hopes to connect the sites through wetlands appreciation

and conservation for all their intrinsic values.

Black-necked stilts are closely allied with American avocets ecologically, and associate with them at breeding sites

and some winter sites. In comparison to the avocets on GSL,

black-necked stilts arrive a week or two later and leave several weeks before (Paton and others, 1992; Paul, unpublished

data). Black-necked stilts winter along the west coast of

Mexico and along the coast of Baja, California. There are

large numbers that winter in the central valley of California

(Shuford and others, 1998). Their breeding ecology, clutch

size, and nesting habitats are similar to those of American

avocets at GSL. Also like avocets, they rely heavily on brine

flies and brine shrimp for food (Hamilton, 1975). Staging

flocks tend to be monotypic even though they are sometimes

folded into a conglomerate of other waterbirds as they forage

and roost. There is often some mixing of species on the margins of the individual flocks. With varying GSL elevations,

some areas important to stilts and avocets can shift because

of inundated or exposed foraging habitat (figure 5).

Snowy Plover

Studies in the early 1990s, and later in 1997, suggest that

more snowy plovers nested at GSL than anywhere in North

America (Paton, 1997; Paton, unpublished data). The snowy

plover and six other subspecies are distributed throughout the

American avocets at Ogden Bay WMA with Antelope Island in the

background. Single-day counts of American Avocets occurring within

the Great Salt Lake ecosystem exceed 250,000 - more than in all other

surveyed wetlands within the Pacific flyway together.

Figure 5. Combined counts of American avocets and black-necked stilts observed during

waterbird surveys on the south arm of the Great Salt lake in 1997 and 1998. For each

year, numbers given represent the range of smallest to largest counts of total individuals

recorded for the survey season during a single visit. Lines on the map demarcate the

boundaries of the survey sites. All surveys were conducted along the lake shoreline.
360 Utah Geological Survey

world. The western snowy plover (C. a. tenuirostris) has two

continental populations: one resident population on the

Pacific coast, and one migratory population in the Great

Basin, inhabiting the salt lakes during the breeding season.

The migratory population is the snowy plover of GSL (Page

and others, 1986). Populations of Great Basin snowy

plovers, including those from GSL, winter on the Pacific

coast along the beaches of the Gulf of California. Snowy

plovers banded in Utah were observed during the non-breeding season at three locations, Puerto Penasco near La Paz, the

Gulf of California, and Scammon’s Lagoon on the west coast

of Baja, California (P. Paton, Utah State University Ph.D.

candidate, personal communication, 1993). In the spring of

1988, the DWR organized surveys to gather baseline information on plover distribution for the GSL ecosystem (Halpin

and Paul, 1989). These surveys produced counts for 1988

and 1989 of 487 adults, 26 juveniles and 845 adults, 53 juveniles, respectively.

Plovers utilize the open shorelines and mud flats of GSL

where they forage considerably on brine flies and other

insects associated with saline soils. They breed and feed in

the same habitat type, even though they may not do both in

the same location (Paton, 1994). GSL is a dynamic system

and it is within the most dynamic component of the lake that

the snowy plover subsists, the shoreline and near-shore

playas.

Plovers begin to arrive at GSL in late March. Males tend

to arrive in the period from late March through early May,

females in late March to mid-June (Paton, 1994). Eggs are

laid mid-April through mid-July. Much detail has been written about the breeding ecology of snowy plovers (Paton,

1994; Paton and Edwards, 1992). Factors of particular

importance to the conservation of snowy plovers on GSL are:

1) all plovers that breed at GSL are migratory and dependent

on habitats outside the scope of GSL management; 2) besides

the breeding population, GSL hosts significant numbers of

transients; and 3) nesting sites and foraging sites for breeding adults are separate and distinct. Some plovers have been

observed greater than 1.9 miles (3 km) from the nest. It appears that the snowy plover is a pioneering species that readily adopts suitable nesting habitat when it becomes available.

Paton’s study sites were all underwater two years before his

research began, yet he found significant breeding and foraging activity in these ephemeral habitats.

Impacts of red fox (Vulpes vulpes) on snowy plovers and

other ground-nesting species of GSL are significant. Predation seems to be a major contributor to plover mortality. The

mean survival rate for an adult plover at GSL is 2.7 years

(Paton, 1994). Paton suggests that if there is a “good” reproductive year every three to five years, the population probably will persist at GSL. 

The most important conservation action for this species,

which at 10,000 individuals represents the single largest

population in the Americas, is the maintenance of undisturbed shoreline that is allowed to fluctuate through seasons

and years. The plover is as flexible as the shoreline is transitory. Paton (1997) pointed out two conditions that have

impacted snowy plover populations along shorelines of GSL

since his original study in the early 1990s. First is the

increased activity of vehicles for recreation or other use.

Two important areas for snowy plovers, Lee Creek and Salt

Wells Flat, have had increased incidences of disturbance by

vehicles. The second condition is the de-watering of some

habitats. De-watering, which has occurred at places like

Deep Creek at Locomotive Springs, has consequences for

plovers as they seek out sites with available fresh water.

Shorebirds Less Understood

There is a plethora of shorebird species for which we

have sketchy information, but for which coarse-scale observations lead one to believe that the GSL ecosystem plays an

important role in their breeding and migratory life history.

Some of these species are the long-billed dowitcher, willet,

black-bellied plover (Pluvialis squatarola), killdeer (Charadrius vociferus), long-billed curlew, greater yellowlegs

(Tringa melanoleuca), lesser yellowlegs (Tringa flavipes),

marbled godwit, sanderling (Calidris alba), least sandpiper

(Calidris minutilla), and western sandpiper. On occasion

some of these species are present in the tens of thousands,

others in the hundreds (Hayward and others, 1976; Paton and

others, 1992; Paul, unpublished data; Paton, unpublished

data; Fellows and Edwards, unpublished data). As the quilt

work of migration is revealed through future studies, there

will most likely be many new revelations concerning GSL’s

function and value to the peregrinations of shorebirds.

Colonial Waterbirds

For the purposes of this paper, colonial waterbirds birds

are those birds for which water resources are an integral part

of their life history, that nest together, and that belong to the

families Podicipedidae, Phalacrocoracidae, Pelecanidae,

Laridae, Ardeidae and Threskiornithidae (Recurvirostridae,

Charadriidae and Scolopacidae are discussed in the shorebird

section). The colonial waterbirds that exist within the GSL

ecosystem are varied and utilize several unique habitats

(table 12). There are 16 species of colonial nesting birds at

GSL, some of which represent the largest single population

known to occur in the world, while others represent a significant proportion of the Pacific flyway or Great Basin populations (table 13).

Colonial waterbirds were among the first birds to be

noted by early Anglo settlers and explorers (Behle, 1958). A

cadre of naturalists, egg collectors, and ornithologists have

explored the GSL islands, starting with John C. Fremont and

Captain Howard Stansbury in the 1840s and continuing with

modern-day biologists, have carried out numerous studies

pertaining to the biology and ecology of GSL colonial waterbirds. The foremost ornithologist studying colonial waterbirds on GSL was William H. Behle. His popular book, The

Bird Life of Great Salt Lake (1958), and other works, have

been foundations upon which many productive studies have

been built.

Colonial waterbirds demonstrate the full range of adaptability to environmental conditions spanning the stenotopic

to the catholic. Some have narrow nesting requirements and

others broad. Some have highly specialized diets and others

are less limited. Their scale of habitat use varies in a single

season from local lake environments to the entire landscape

of the Great Basin and beyond. It is for these varied reasons

that GSL colonial waterbirds are such compelling subjects.

The GSL eared grebe (Podiceps nigricollis) staging population represents nearly half of the North American continental population. American white pelican, white-faced ibis,
Great Salt Lake - An Overview of Change 361

and California gull populations at GSL each represent the

largest, or nearly largest, in the world (table 13). There are

several elements that contribute to this. The magnitude of

the ecosystem, the richness of food resources, and the security from terrestrial predators are all paramount reasons for

the success of these populations and the motivation for birds

to nest in colonies. Other species’ populations are also large,

but comparative data to assess their value is not available.

Some of these include the western grebe (Aechmophorus

occidentalis), double-crested cormorant, snowy egret (Egretta thula), Franklin’s gull, and Forster’s tern (Sterna forsteri).

For some of these species, baseline data from GSL is missing. Colonial waterbird species that are often found in significant numbers during the post-breeding season include

Franklin’s gull, Bonaparte’s gull (Larus philadelphia), ringbilled gull (Larus delawarensis), and black tern (Chlidonias

niger) (Paton and Edwards, unpublished data; Paul, unpublished data).

The 1980s Flood Years’ Effect on Colonial Waterbirds

All 16 species of GSL colonial waterbirds that regularly

breed here are subject to the vagrancies of lake dynamics.

These species colonial nesting habitats were profoundly

affected by the flood years of the 1980s. In 1987, the lake

reached its historic high of 4,211.85 feet (1,283.78 m) above

sea level, compared to the average long-term elevation of

approximately 4,200 feet (1,280.16 m) above sea level.

Because of the lake’s low-gradient bottom and the amount of

shore, the upland and wetland area covered with water increased by 46 percent. This caused extensive flooding of all

the state WMAs near the lake and the BRMBR.

The rapid lake-level rise in the 1980s, brought on by

unseasonably wet winters and wet cool summers, was

unprecedented. Historically, the lake was dynamic, but had

never reached elevations higher than 4,207 feet (1,282.29 m)

above sea level during the 20th century. Salt water inundated many low-relief nesting islands, flats, bars, and dikes that

hosted emergent, wetland nest sites (the south arm’s salinity

was 57 ppt). Riparian forests were flooded, and shoreline

bird colony sites were covered. The complexion of the lake

shoreline changed from a varied ecosystem matrix of saltwater habitats and diverse associated wetlands, to a lake with a

well-defined shoreline.

The effects of flooding on most colonies were negative ,

but for some, it was beneficial. In 1982, 15 colonies of California gulls contained 49,862 breeding adults. During the

1983 breeding season, 14 colonies were occupied by 80,487

breeding adults (Paul and others, 1990). Between the 1982

and 1983 nesting seasons, GSL had risen approximately two

feet and flooded several of the 1982 colonies, but in 1983,

several new colonies were created and some historic nest

sites were reoccupied after years of dormancy. There was an

amazing 61 percent total increase in breeding adults at GSL.

While the rising lake negatively affected some nest colonies

by covering them with water, it appears that nesting substrate

was not a limiting factor and the wetter conditions may have

enhanced food resources for this highly adaptable species.

Another suite of bird species that seemed to benefit, or

experienced little impact, from the flooding was herons and

egrets (Family Ardeidae). The flooding of riparian forests

and tamarisk-lined dikes provided a more secure nesting

environment, especially in the Ogden Bay and Howard

Slough areas of the Weber River Delta, the flooded Jordan

Table 13. Population size of notable adult breeding colonial water birds for the Great Salt Lake, Utah (unpublished UDWR data files).

Species Peak Numbers Ten-Year Range/Numbers Data Source

California gull 156,000 1982-1991/76,000-156,000 DWR, (Paul 1990)

American white pelican 20,270 1988-1998/8,326-20,270 DWR unpubl. reports

White-faced ibis 60,000 1988-1998/7,400-60,000 (data missing) USFWS/DWR unpubl. data

Table 12. Breeding colonial waterbird species and nesting habitats/substrates used at the Great Salt Lake (colonial shorebirds not included)

(from unpublished UWDR data files).

Nesting Habitats/Substrates

Islands Mud Flats/ Matted Emergant Shrubby: in Trees: Human-made

Sand Bars Submergant Vegetation or near water near water

Vegetation

American white Ring-billed gull Western grebe Snowy egret Great blue heron Double crested Double-crested 

pelican cormorant cormorant

Double-crested California gull Clark's grebe Cattle egret Snowy egret Great blue heron Great blue heron

cormorant

Great blue heron Caspian tern Forster's tern Black-crowned night Cattle egret Snowy egret Ring-billed gull

heron

California gull Black tern White-faced ibis Black-crowned night Cattle egret California gull

heron

Caspian tern Franklin's gull Black-crowned night Caspian tern

heron

Forster’s tern Forster's tern

Black tern Black tern
362 Utah Geological Survey

River Delta, and other lake-wide scattered sites (figure 1).

Many of these sites had dikes and roads which, when available to human traffic and disturbance, precluded nesting before the high lake years. This disturbance was eliminated as

travel ways were flooded. Since 1987, as the lake receded,

roads were made useable again and herons abandoned nesting in these areas. There is no baseline nesting data prior to

1983 to determine if great blue herons, in particular, may

have simply been displaced from secure island sites to flooded trees. Unfortunately, alternative nest sites were not available for most ground and emergent vegetation nesting colonial species such as the white-faced ibis, Franklin’s gull,

Forster’s tern, American avocet, and black-necked stilt. 

Food resources for colonial birds are affected in significant ways when the lake waxes and wanes with climatic conditions. Piscivorous colonial waterbirds are influenced geographically with regard to flooding on GSL (Flannery, 1988).

At the lake’s peak level in 1987, state WMAs in the south

arm that normally held healthy populations of freshwater

fish, carp (Cyprinse carpio) in particular, were inundated

with brines of 60-70 ppt which killed fish. In the northeast,

Bear River Bay, Willard Bay, Harold Crane WMA, BRMBR,

and associated private duck hunting clubs all became one

enormous fishery. Consequently, this was the only remaining extensive pelican foraging habitat on the lake (Flannery,

1988). With the exception of rivers and small streams, this

was true for most other fish-eating birds. Some species, such

as the western grebe and Clark’s grebe (Aechmophorus

clarkii), moved to nearby Mantua Reservoir and other freshwater fisheries. These alternative sites, and the anthropogenically influenced GSL regions like the Gunnison Bay,

provided some diversity for birds at this time of ecosystem

turbulence. The north arm played a role as a waterbird haven

during the high lake years. In 1986 and 1987, lowered salinities in the north arm hovered around 160-170 ppt, becoming

the only part of the lake which produced a robust brine

shrimp population. Consequently, the Gunnison Bay was the

primary staging site for Wilson’s phalaropes and eared

grebes during those years (DWR, unpublished data).

Some GSL breeding species had more trouble contending with changing or adverse conditions because they couldn’t find alternative sites and were unable to breed, or forced

to simply disperse. They are the white-faced ibis, Franklin’s

gull, American avocet, black-necked stilt, snowy plover, and

Forster’s tern. Even though some of these species managed

to nest within the system during high lake years, their numbers were dramatically diminished. All of these negatively

affected waterbirds were easily impacted by flooding or

high-lake conditions because they either nest on or near the

ground, or in emergent vegetation near GSL.

A long-term prospectus is necessary to appropriately

assess the effect of fluctuating lake conditions for these

breeding species. The saltwater intrusion which periodically

damages emergent vegetation during high-water cycles is the

same disturbance that maintains open beaches and mud flats

along other lake margins. For those species nesting in, or on

the margins, of hardstem bulrush, alkali bulrush, cattail, and

common reed (Phragmites australis), such as the whitefaced ibis, Franklin’s gull and Forster’s tern, flooding can be

devastating during a nesting season. Snowy plovers, American avocets and black-necked stilts, however, benefit in the

long term from disturbances that create or maintain open

shorelines. Saltwater inundation also can have some longrange positive effects on wetlands. Flooded and salt-burnt

vegetation most often dies after prolonged salt water exposure. A productive emergent marsh is one in flux, or one in

an early stage of vegetative succession. These pioneering

wetlands provide more edge and structural diversity than do

rank old stands.

An excellent example of the evolution of a saltwater

inundated wetland is the West Layton/Kaysville Marsh (figure 1) that occupies a near-lake location in western Davis

County. For several decades this wetland had an immense

emergent component of hardstem and alkali bulrush providing nesting habitat for white-faced ibis, Franklin’s gulls, and

many other marsh birds. In 1978, several thousand nests of

ibis and Franklin gulls were observed by D. Paul and S.

Manes (DWR, personal communication). In 1983, there were

no nesting ibis at the Layton/Kaysville Marsh. By 1986, this

emergent nesting habitat was essentially lost to lake water

inundation. The only emergent vegetation remaining

rimmed the area to the north and east. This was a typical

scene for many of GSL’s wetlands. (See photographs in the

color photograph section for a visual account of the effects of

lake dynamics on shoreline and wetland habitats in the west

Layton area). By 1987, the lake had swelled to 4,211.85 feet

Photo 6. White-faced ibis family at Layton Wetlands during the 1998

nesting season. Ibis colonize flooded wetland stands during years

when the lake elevation is above the long-term-elevation average.

During average low-lake years (<4,200 feet), this Layton area has an

extensive bar that extends into the lake away from the wetlands which,

under those conditions, supports hundreds of avocets and other shorebirds.
(1,283.77 m) above sea level. By February 1989, it had

dropped to 4,206.45 feet (1,282.13 m) above sea level and it

continued to drop near 4,200.00 feet (1,280.16 m) in 1992.

In 1990, the Layton/Kaysville Marsh was a barren plain

of dead bulrush stubble transected by drainages from irrigation run off. Soon, the moist salt-saturated hydric soils became alive with brine flies. These flies used acres of bulrush

stems as seven-inch vertical habitat upon which they foraged, rested, and in places where the stems were still underwater, pupated. In less than a decade, this once dead emergent wetland metamorphosed back into one of the most spectacular shorebird habitats on the lake, and perhaps in North

America. Hundreds of thousands of Wilson’s phalaropes,

American avocets, black-necked stilts, snowy plovers, and

other species glutted themselves on brine flies. It was during

these post-flood years that the greatest numbers of Wilson’s

phalaropes were recorded for GSL (figure 6), some 200,000

of which foraged on this vast salt plain of brine flies in the

Layton/Kaysville Marsh.

In time for the arrival of northern shovelers and greenwinged teal at the end of the 1992 growing season, green ribbons of emergent vegetation defined the drainage courses as

they wound through the open flats of the Layton/Kaysville

Marsh. By the end of 1993, the landscape had significantly

changed as riparian strings of rushes broadened out into

stands that began to fill open spaces. Paton’s record of the

rapid and profound changes in snowy plover habitat in the

Layton/Kaysville Marsh area during the period from 1990

through 1993 is a stellar example of the lake’s wetland

dynamics. The snowy plover is the consummate mud flat,

open-shoreline shorebird of GSL. From 1990 to 1993,

potential plover nesting habitat had declined by 74.7 percent.

The reason nesting habitat declined was primarily due to the

re-establishment of vegetation (Paton, 1994). By 1995, the

Layton/Kaysville marsh looked very much like the emergent

marshes of 1978-1982. In 1998, a thorough count of whitefaced ibis nests in two colonies at the marsh site came to over

6,000 individual nests (DWR, unpublished data). Also found

nesting in the two ibis colonies were Franklin’s gulls and

Forster’s tern. Snowy egrets and cattle egrets (Bubulcus ibis)

nested nearby in a common reed bed. Currently, fall numbers of waterfowl associated with the West Layton wetland,

and near-lake environments, are in the tens of thousands.

Within two recent nesting seasons and a lake elevation difference of two feet, there have been changes in this area. In

1997, there was a defined shoreline with a sand/mud bar on

the edge of the Layton/Kaysville Marsh which was used by

thousands of avocets and other shorebirds. In 1998, the lake

had risen, obliterating the shoreline and establishing excellent nesting conditions for ibis (figure 7) (Paul, unpublished

data). The most notable difference between the 1978 West

Layton emergent vegetation (hardstem and alkali bullrush

dominant) and 1997-98 vegetation was the increase in common reed.

The circumstances surrounding the event of migration

provide the greatest problems in estimating populations of

migrating colonial nesting birds. What happens to displaced,

emergent vegetation, nesting species during high-lake elevation years is a conundrum. It is certain that ibis continued to

nest in the eastern and northern portions of Bear River Bay,

and in other small wetlands, when the lake was above 4,211

feet (1,283.51 m) above sea level, but not in the same numbers as in years before the flood years of the 1980s. In 1985,

150 pairs of white-faced ibis nested in the Cutler Marsh of

Cache Valley, Utah. In 1989, at this same location, nesting

pairs were estimated at greater than 2,000 (Bridgerland

Audubon Society survey coordinator, personal communication, 1989). Between 1984 and 1988, increases in whitefaced ibis numbers were noted at wetland sites in Nevada and

Oregon, and to a lesser degree in Idaho (B. Sharp, USFWS,

personal communication, 1999). At these western Great

Great Salt Lake - An Overview of Change 363

Photo 7. White-faced Ibis provides shade for young nestlings.

Figure 6. Total counts from annual surveys of Wilson’s phalaropes

during their peak staging period in relation to lake elevation on the

Great Salt Lake, Utah, 1982-1998 (some years not surveyed).
364 Utah Geological Survey

Basin wetland sites, an increase in moisture occurred from

the same wet cycle affecting GSL. Was the increase in ibis

numbers due to improved local wetland conditions at these

areas of the Great Basin, displacement of birds from the large

breeding colonies of GSL when wetlands were so flooded, or

a combination of these two situations? Recent cooperation

and coordination among states of the Great Basin will assist

in better understanding how colonial waterbirds play out

their life strategies within the limits of their movement patterns during and between seasons (Haig, 1998).

Important Colonial Waterbirds of Great Salt Lake

Eared grebe: Eared grebes are circumpolar in their distribution with the North American population, breeding from

the Great Plains of Canada and the United States into the

Great Basin. They winter from the Salton Sea, south into the

Gulf of California. Between the breeding grounds and wintering sites, most eared grebes spend time at large saline

lakes during the molt migration which takes place when birds

move away from the nesting grounds, at which time they

molt flight feathers and replace them with fresh ones. Recent

population studies demonstrate that most of the eared grebes

on the continent molt and stage at two salt lakes in the Great

Basin - Mono Lake, California and the Great Salt Lake, Utah.

Slightly larger numbers occur at Mono Lake at this time; in

1996 and 1997, the Mono Lake grebe population was estimated at 1.5 million and 1.6 million grebes, respectively,

with a 5 percent error (Boyd and Jehl, 1998). During 1997

on GSL, using similar survey methods, 1.5 million grebes

were estimated within a 4 percent error (Paul and others,

1998a, b). Eared grebes breed and nest within the GSL system in areas with submergent and emergent vegetation

(where nest material and substrate can be found) and where

optimal conditions exist for wave and wind abatement to prevent disturbance to their nests. Subsequently, there are eared

grebes associated with the lake in all seasons except midwinter. The known breeding population ranges between

1,000 and 3,000 adults (DWR and USFWS, unpublished

data). However, GSL’s most important role for eared grebe

conservation occurs during the fall migration. Because of

the vast numbers involved, eared grebes at GSL must accumulate from many localities in North America. Evidence for

this includes radio-marked, eared grebe adults from British

Columbia being relocated at GSL in fall. A two-year old bird

that was banded by J. R. Jehl, Jr. at Mono Lake in 1996 was

recovered on GSL in October 1998, suggesting that eared

grebes move between salt lakes within the Great Basin.

Eared grebe molt migration begins at the end of August.

GSL peak numbers are believed to occur between mid-October and the first of November (Paul and others, 1998b).

From eared grebe downing data and field observations, we

know that eared grebes depart GSL, in most years, between

early December and early January (Jehl and others, 1998).

Eared grebe downings are well-documented reoccurring events that most often are associated with winter storms at

night. Eared grebes are night migrants and appear to become

confused in inclement weather. They often land under these

conditions on lighted roads and other hard surfaces resulting

in death in large numbers. These lighted wet surfaces appear

to give the appearance of water to landing grebes.

Data from 1992 and 1997 describe body composition of

eared grebes at GSL (Jehl, 1998). This data indicates a mean

body mass of 375 ± 50g for males, and 325 ± 50g for females

upon arrival in August. By December 1, males and females

are 575 ± 25g and 500 ± 50g, respectively. During this time

period, the data demonstrated an increase in leg and heart

mass through the fall, as well as a concomitant increase in the

size of digestive organs. At the same time, all remige and

most covert feathers were dropped simultaneously, rendering

Figure 7. Numbers of black-necked stilts (BNST), American avocets

(AMAV), and white-faced ibis (WFIB) in relation to lake elevation at

the Layton-Kaysville Marsh, Great Salt Lake, Utah, 1997 and 1998.
Great Salt Lake - An Overview of Change 365

the grebe flightless for a period of 35 to 40 days. The synchronous molt and body mass increase, aided by increased

size of viscera, demands an abundant food source to sustain

these processes. Before grebes depart, they may lose 25 percent of peak body mass as they condition for migration (Jehl,

1998). Migrating weights were obtained from eared grebes

that came down in a January 1998 storm in the vicinity of

Fillmore, Utah. The mean for males was 420.8 grams (46.82

standard deviation) and 377.1 grams for females (35.60 standard deviation) (Jehl, 1998). It appears that since eared

grebes do not use these weight gains for energy during

migration, they are amassed to hedge against nutritional

needs while flightless for a month or more as they generate

new flight feathers.

Stomach contents of eared grebes collected from GSL in

1992 and 1997 during September through December

revealed, with rare exception, that grebes fed exclusively on

brine shrimp. Some birds examined in late August and early

September had fed on brine fly larvae as well as brine shrimp

(Jehl, 1998). Brine shrimp cysts were found in gizzards of

grebes examined in December, but all were associated with

bits of tissue from brine shrimp adults, and were most likely

a result of foraging on gravid adult female shrimp and not

selected as such. Intestinal contents of ten grebes were determined. Of these grebes, there were thousands of cysts in the

gizzard, but there were no more than two to three cysts in any

intestine of a single bird. Cysts are most likely retained and

digested along with adult shrimp. The food value of cysts

remains to be determined through bomb calorimetry.

Years of fall GSL grebe surveys have demonstrated that

this species keys in on areas of the lake with high densities

of brine shrimp. At present, the lake’s grebe population continues to be large and represents a significant portion of the

western hemisphere’s population.

California gull: There are three species of gulls (Family

Larinae) that breed at GSL, Franklin’s, ring-billed, and California gulls. The California gull, Utah’s state bird, breeds

within the GSL ecosystem in larger numbers than anywhere

else in the world. Recent breeding season estimates are

greater than 150,000 breeding adults (DWR unpublished

data). This is a significant increase over the 94,000 to 99,000

breeding adults of the late 1980s (Paul and others, 1990).

Behle (1958) noted an increase in California gull nesting

activity along the eastern edge of GSL, especially at the state

WMAs and other man-made environments. This increase

was noted in the late 1940s and 1950s in comparison to his

original surveys in 1938. Behle’s 1931 estimate of 80,000

adult California gulls was the first attempt to enumerate the

breeding population on the lake. Behle’s impression was that

the lake’s California gull population had not increased over

the time period from 1930 to 1950, but he noted increased

gulls nesting in new east-lake habitats. Fifty years after

Behle’s first all-lake breeding adult survey, another all-lake

survey was completed by Paul and other DWR personnel

wherein nearly 50,000 adults were observed nesting on the

lake in 1982. Then in 1983, 80,000 adults were counted

(Paul, 1984), and by 1991 there were 156,000 gulls (DWR

unpublished data).

There are several reasons that have contributed to the

recent increase in California gull habitat and breeding adults.

California gulls, like many gull species, seem to thrive in the

presence of man. They follow the plow, exploit parks and

parking lots for food scraps, and forage at landfills. In addition to exploiting food resources in urban and rural environments, they readily accept appropriate man-made structures

as nesting habitat. Some examples of these man-made structures include dikes and habitat islands at state WMAs, levees

along solar evaporation ponds and dikes and protective

breakwater structures associated with sewage lagoon ponds.

The largest California gull colony in the world, comprised of

57,265 breeding adults, occurs within the dike and island

complex of a salt company on the south end of GSL. Therefore, the combination of readily available food and close

proximity to secure anthropogenically enhanced nest sites is

a major reason for increased breeding activity at GSL. A

study in the early 1980s (Winkler, 1983) of the two California gull populations at GSL and at Mono Lake, California

found that the Mono Lake population consistently produced

smaller clutch sizes. The mean clutch size at Mono Lake was

two, while at GSL it was three. The study suggested that the

reduced clutch size at Mono Lake was due to the lack of

nearby early spring food resources necessary for the production of additional eggs. Mono Lake sits at a higher elevation

near the Sierra Nevada range, and has a paucity of humanprovided food resources available to gulls.

Aside from the man-induced values, GSL resources are

still paramount in supporting the ecosystem’s robust California gull population. California gulls are omnivorous and

opportunistic foragers. They exploit lucrative resources in

large flocks and with considerable tenacity. They rely on

GSL’s macroinvertebrates, particularly as they occur in periods of seasonal abundance. Remote colonies of GSL, like

Bird and Gunnison Islands, forage for brine shrimp and brine

flies in the same, or nearby, locale to reduce energy expenditure in flight travel associated with food gathering. During

summer and fall, when and where there are dense populations of brine flies, large numbers of California gulls, often

in excess of 20,000 individuals, will gather to forage with

masses of other waterbirds. At times, gulls can be seen running down the shoreline, mouths agape, through swarming

adult brine flies, gathering up flies much like a vacuum

cleaner.

Migration patterns of California gulls from GSL were

determined by an intense banding effort in the 1930s and

1940s. Approximately 13,700 banded gulls produced 236

returns. Most birds were banded at Farmington Bay WMA

and at Egg Island. The results of this banding demonstrated

that birds winter on the west coast from Vancouver down to

the Baja Peninsula, with the majority found in the states of

California, Oregon, and Washington (Behle, 1958).

It is important to keep in mind that a large population of

a single bird species seen at GSL is not necessarily an indicator that all is well. What one sees at GSL may be the

largest concentration in the world of that species at that time,

as is the case for the California gull. However, observers are

not seeing the same species in the same large numbers on the

Great Lakes, or the Caspian Sea, or any other place in the

world where said species may occur.

American white pelican: Currently there is only one colony

of breeding American white pelicans in Utah. It occurs on

Gunnison Island and represents one of the largest breeding

populations in North America. In surveys conducted in the

1970s of colonies, it ranked second (Rawley, 1976). During

the late 1980s and early 1990s, record numbers of breeding
366 Utah Geological Survey

adults occurred on Gunnison Island (figure 8). The GSL

colony is important not only because of its population size,

but also because of its security. Gunnison Island is

sequestered in a remote location in the north arm of GSL,

safe from boat traffic and other potential human disturbances. The island is protected by law as a wildlife management area. Under statute, it is closed to trespass during the

nesting season except for purposes of wildlife conservation

as administered by DWR.

Human disturbance is the main cause of colony desertion

by pelicans in North America and other parts of the world.

Another major cause of desertion is the presence of terrestrial predators at times when colonies become accessible via

land bridges at low-water levels. These two reasons are the

cause of desertion by other American white pelican colonies

in Utah (Behle, 1944; Knopf, 1975). Other Utah colonies

that have since been deserted are: 1) Hat Island (a.k.a., Bird

Island), which was last known to be active in 1943; 2) Egg

Island, which was observed as a colony by Howard Stansbury in May of 1850; and 3) Badger Island, which was

reported to have nesting pelicans by Dr. H. A. Whytock in the

1880s (Behle, 1944). Rock Island on Utah Lake was reported in 1904 as possessing 200 pelican nests with young

(Goodwin, 1904). Each of these potential colonies have been

impacted by proximal human or predator presence.

Pelicans are piscivorous, thus presenting a logistic challenge to Gunnison Island inhabitants. The nearest fishery is

roughly 30 miles (48 km) away, across the Promontory

Mountains into Bear River Bay. This means a minimum 60

miles (96 km) round-trip flight for foraging adults (which

must negotiate the 2,300-foot (700 meter) vertical lift of the

Promontory Mountains with a stomach full of fish) to feed

their young on Gunnison Island. Pelicans at Gunnison Island

are known to make fishing forays as far north as American

Falls Reservoir, and as far south as Utah Lake (Flannery,

1988). These are trips in excess of 186 miles (300 km).

Breeding population information is sketchy through

time, but recent Gunnison Island surveys showed increases

in numbers since 1980 (figure 8). These increases may

reflect the importance to pelicans of introduced carp, gizzard

shad (Dorosoma cepedianum), and other non-indigenous

fishes into the Wasatch Front fisheries. Studies at foraging

areas of white pelicans further confirm the current reliance

on carp as an important component of the diet of GSL

ecosystem pelicans (Flannery, 1988; Paul and others, unpublished data). Carp thrive in nutrient-rich shallow-water systems of the waterfowl management areas and freshwater

bays, for example, the Willard Spur and Bear River Bay. Pelicans are communal foragers and excel in the exploitation of

shallow fisheries. Before carp were present, there were small

indigenous chubs and shiners found in the ecosystem. This

helped to support the local pelican population, but probably

not to the extent that the large freshwater impoundments of

the waterfowl management areas did with their fecund populations of non-native fishes. This enriched environment and

the secure nest site of Gunnison Island are the most likely

factors lending to the increased numbers of breeding American white pelicans at GSL.

Since the 1930s and 1940s, when a significant effort was

made to band pelicans at Gunnison Island by Wm. Behle,

Jess Low, and others, there has been some additional banding in the region by others. Pelicans nesting at GSL winter

along the west coast and interior of Mexico. Of 1,502 young

banded during the 1930s and 1940s, more than 80 bandreturn observations were made (Behle, 1958). In 1996 and

1997, notable efforts to learn migration patterns of pelicans

included a project involving tracking by satellite telemetry

from Stillwater NWR in Nevada (Fuller and others, 1998).

After one month, a radio-marked pelican flew from Stillwater NWR, Nevada, to Malheur NWR, Oregon, and then to

Payette, Idaho. In mid-September this same bird flew to

GSL, to the Salton Sea, California, and finally reached Colima State, Mexico by the following December. Seven weeks

after capture, another radio-marked pelican flew from Stillwater NWR, Nevada to Cache Valley, Utah. By October, it

was at the Salton Sea. Of 17 birds marked with satellite radio

transmitters, five wintered at the Salton Sea and six made it

to Mexico. This telemetry study has strengthened an observation made from Behle’s banding project 50 years ago - the

curious behavior of a northward movement from Great Basin

banding sites before a southward winter migration. Several

birds banded on GSL traveled north to southeastern Idaho

(Behle, 1958), just as several birds banded at Stillwater

NWR traveled north before finally wintering south.

White-faced ibis: GSL harbors the largest breeding population of white-faced ibis in the Great Basin, and perhaps in the

continental United States. White-faced ibis are emergent

marsh nesters, often keying in on hardstem bulrush as a nest

substrate. Alongside Franklin’s gulls, they nest in colonies

which range from a few pairs to as large as several thousand

pairs (Sharp, 1985). Nesting habitats, comprised of stands

of emergent vegetation, occur in standing water. Water

serves at least two functions in the colony. It reduces access

by mammalian predators and supports growth of emergent

vegetation for nest material and substrate. The nature of this

nesting habitat type fosters nomadic and opportunistic nesting behavior due to the ephemeral nature of the lacustrine

emergent wetlands within the GSL ecosystem, and at other

wetland sites characteristic to the Great Basin. As shorelines

flood and recede, and as weather patterns shift between wet

and dry, emergent stands gain or lose their attractiveness to

ibis as colonial nest sites. For these reasons, basin nesting

ibis seem to shift colony sites often within local marshes as

well as between Great Basin wetlands (Sharp, 1985; Kelchin,

Figure 8. Estimates of nesting adult American white pelicans at Gunnison Island, Great Salt Lake, Utah, 1963-1998 (some years missing).
Great Salt Lake - An Overview of Change 367

1998). An example of intermittent white-faced ibis breeding

at the west Layton/Kaysville wetland complex is described

earlier in this article.

Even under the worst nesting conditions, as in the highwater years of the mid-1980s, GSL’s breeding population of

ibis persisted, but often in reduced numbers. During the mid1980s, the lake population was reduced to hundreds of pairs,

but the same wet water cycle improved emergent vegetation

nesting conditions around the region. Sites such as Carson

Lake, the Ruby Marshes and Stillwater NWR, Nevada; Malheur Lake, Oregon; Mud Lake, Idaho; and the Cutler Marsh,

Utah all witnessed an increase in available nesting habitat

and subsequent breeding white-faced ibis. The evidence is

only anecdotal, but it does suggest that as conditions change,

ibis move within the region to colonize and nest. Since the

early 1990s, white-faced ibis have nested in large numbers at

several wetlands around GSL. Thousands of nests have been

identified in the Bear River Bay complex, the west Layton/Kaysville complex, and Farmington Bay wetlands. An

estimated 25,000 to 30,000 nesting pairs occurred at GSL

annually during 1996 through 1998 (DWR and USFWS,

unpublished data).

White-faced ibis often forage away from their nest

colonies in flood-irrigated pastures and alfalfa fields, which

are nearly all located on private land. Stomachs of whitefaced ibis in Utah revealed a preference for insects, especially the larvae and adults of Diptera and Coleoptera and earthworms (Capen and Low, 1974; Steele, 1980). Discovering

this selective foraging behavior, conservation efforts need to

address possible impacts to upland agrarian habitats such as

urbanization of farmlands, and switching from flood irrigation to pressurized water systems, and how these changes

may affect white-faced ibis.

White-faced ibis winter around inland lakes of northcentral Mexico, on the coastal plains of Mexico, and in the

Sacramento, San Joaquin, Coachella, Imperial and Colorado

River valleys of California (Shuford and others, 1996). It is

known that significant private lands are being used by wintering ibis in these areas.

In summary, it is apparent when considering conservation strategies for white-faced ibis that several factors are

especially important to keep in mind. Historical colony data

demonstrates that colonies reoccur at the same location

through time even when the site is flooded or desiccated periodically. Judgements of a nest’s site value must always be

made with regard to its potential and not its present condition. For this reason, it is imperative to document colony

locations from year to year. Most ibis colony sites are used

by several other species as well, such as Franklin’s gulls,

Forster’s terns, snowy and cattle egrets and black-crowned

night herons (Nycticorax nycticorax hoactli). So, protecting

a site for ibis protects the site for multiple species. A second

important consideration is the preservation of farmland and

farming activities that utilize flood irrigation of pastures and

fields. These unique flooded areas provide an important and

unique foraging habitat for white-faced ibis and Franklin’s

gulls. Flood irrigation provides an abundance of earth

worms and other invertebrates that rise to the soil surface and

are easily made available to foraging birds. Outside of the

California gull, the white-faced ibis may be the most readily

recognized and admired marsh bird in Utah because it is so

often seen flying through our towns to and from its breeding

colonies as it forages near rural towns and on farms.

GSL ECOSYSTEM AND AVIAN

CONSERVATION

History Of Habitat Management On GSL

GSL has a rich history of management activities related

to waterbirds and their habitats. Although harvest regulation

is a major and important management activity for waterfowl

species, we will not describe regulation processes or their

history in any detail in this discussion.

Early actions to preserve wetland habitats around GSL

are detailed by Nelson (1966). Sportsmen’s groups began

organizing hunting clubs in the 1890s and were among the

first to initiate land acquisitions with the intent to protect

waterfowl habitat. The Jordan Fur and Reclamation Company was likely the first hunting club organized upon statehood

in 1896, hence its commonly used name “Newstate.” Other

prominent clubs were organized around 1900 and still operate today including the Bear River and Chesapeake clubs on

the Bear River delta, and the Burnham Club on the Jordan

River delta. Numerous other clubs were established over the

next 50 years, many utilizing water sources from smaller

streams and agricultural/municipal return flows and surpluses. Because the state does not require clubs to be licensed,

no lake-wide accounting of duck club acreage is available

today. Information from Jensen (1974) is the most recent

estimate and indicates about 50,000 acres (20,235 hm2) of

land is incorporated in private hunting clubs on GSL.

The state initiated its first acquisition and management

of important wetlands in 1923, with the purchase and development of Public Shooting Grounds WMA. As its name implies, preserving public hunting opportunities during a time

when private clubs were incorporating the best areas was the

motivating reason for this development. In the 1930s, the

state expanded its formal presence with establishment of

Farmington Bay, Ogden Bay, and Locomotive Springs

WMAs. New state areas were created, and existing areas

expanded during the period from 1950 through the 1990s.

The DWR currently manages eight WMAs encompassing

over 80,000 acres (32,376 hm2) on the margins of GSL (figure 9).

The DWR also has state management authority to use

any, and all, unsurveyed state-owned lands below the 1855

surveyed meander line of GSL, within certain townships, for

the creation, operation, maintenance, and management of

wildlife management areas, fishing waters and other recreational activities (Utah Code Ann. Sec. 23-21-5). This management authority now covers approximately 487,000 acres

(197,089 hm2) of lake bed (figure 9). This statutory dedication of sovereign state lands for wildlife management

extends as far back as 1943, even though ownership of the

bed of GSL was unresolved until 1976, when a U.S. Supreme

Court decision gave clear title to the state for lands below the

meander line.

In the late 1970s, action was taken by the DWR and state

legislature to purchase two important bird colony islands on

GSL, Gunnison, and Hat (Bird) islands. These islands were

purchased and are managed as WMAs by DWR. Utah rules

protect them from human disturbance during critical nesting

seasons.

Federal management on GSL centers around the

BRMBR, which was established in 1929, in part, to help con-
368 Utah Geological Survey

trol avian botulism. This refuge currently covers over 75,000

acres (30,353 hm2) of land, and is the largest management

block on the Bear River delta. The Bureau of Land Management also administers numerous sections of land around

the north, west, and southwest shores of GSL, and actively

manages approximately 11,000 acres (4,452 hm2) of habitat

within the Blue Springs and Salt Wells Wildlife Habitat

Areas created during the 1980s and 1990s.

Federal presence on GSL was expanded in 1992 with the

authorization of the Central Utah Project Completion Act,

and the subsequent establishment of the Utah Reclamation

Mitigation and Conservation Commission in 1994. This act

provided funding to complete water development projects

authorized in earlier legislation, but also provided funding to

mitigate for the project’s environmental damages. This act

provided 14 million dollars for wetland acquisition, restoration, and enhancement in and around GSL during the 1990s

and among other things, greatly facilitated the rebuilding of

Farmington Bay and Ogden Bay WMAs.

Non-government organizations also have a significant

presence on GSL, with the Nature Conservancy’s 1,696 acre

(686 hm2) sanctuary (located within the Layton-Kaysville

Marsh), initiated in 1983, and the National Audubon’s 1,400

acre (567 hm2) Gilmore Sanctuary on the south shore, initiated in 1992. Several managed mitigation projects protect

wetlands created on the south shore, most notedly the 450

acre (182 hm2), $12 million dollar Salt Lake International

Airport Wetland Mitigation area, and the 3,800 acre (1,538

hm2) Inland Sea Shorebird Reserve established by Kennecott

Utah Copper. Ducks Unlimited has been active in habitat

conservation throughout most of the 20th century, and began

funding waterfowl habitat projects in Utah with their Matching Aid to Restore States Habitat (MARSH) program, initiated in 1985. The MARSH program has provided $226,000

for habitat protection on over 25,000 acres (61,774 hm2) of

habitat since 1986, most of which has been focused on GSL.

Several other significant conservation actions impacted

migratory bird management and protection in Utah during

the 20th century (table 14).

Although wetland acquisition and preservation was a

Figure 9. State Waterfowl Management Areas (dark shading), and lands codified for wildlife management purposes (medium shading) on the Great

Salt Lake, Utah.

Locomotive Springs WMA

Salt Creek WMA

Public Shooting Grounds WMA

Harold Crane WMA

Ogden Bay WMA

Howard Slough WMA

Layton Kaysville Marsh WMA

Farmington Bay WMA Timpie Springs WMA
Great Salt Lake - An Overview of Change 369

significant and key component of management throughout

the 20th century on GSL, development and manipulation of

those same lands share an equally important and informative

history. Smith and Kadlec (1986), and Nelson (1954) detailed much of the history of agency actions on acquired

lands through the early 1980s and is the basis for part of the

following chronological summary. 

In the early 1900s, most of the fresh-water marshes in

GSL existed on natural deltas of the Bear, Weber, and Jordan

rivers of the east shore. There also were emergent wetlands

associated with smaller streams and springs, but they

undoubtedly were proportionately small. The vast majority

of the GSL shoreline was likely a mud flat, remnants of Lake

Bonneville, and too salty to support most plant species. Historical accounts suggest the marshes supported myriads of

waterbirds, but were also plagued with enormous disease

losses from avian botulism. Agency actions were subsequently focused on acquiring land and water in the delta

areas, and capturing the flows through diversions and dike

developments. The result was a vast expansion of fresh

water marsh area, stabilization of water levels in many delta

areas, and an apparent reduction in the magnitude of disease

losses. Dramatic increases in the abundance of breeding

birds and offspring were also noted during the early development period. Stabilized water levels, however, eventually

converted diverse and desirable vegetative communities to

dense, monotypic stands of cattail and other less-desirable

plants. Waterfowl breeding populations and production declined in response to maturing marshes.

Concerns over declining marsh productivity led to a

period of research and experimentation on management areas

in the 1960s and 1970s by DWR wetland managers. These

studies were directed toward identifying water needs and

salinity tolerances of plants as well as management techniques useful in controlling plant succession. Initiation of

additional research and implementation of successful manTable 14. Some major conservation actions affecting migratory bird populations on the Great Salt Lake during the 20th century.

Year Conservation Action Purpose

1918 Migratory Bird Treaty Act Regulated the take, propagation and possession of migratory birds.

1934 Migratory Bird Hunting Stamp Act Established the federal duck stamp to fund habitat acquisitions.

1937 Federal Aid in Wildlife Restoration Act Tax on firearms and ammunition to fund state wildlife restoration activities.

Has provided more than $17 million for the GSL activities.

1977 Clean Water Act Protects aquatic ecosystems. Sec. 404 requires permits to discharge fill 

materials into wetlands.

1985 Ducks Unlimited MARSH program Provides private funding to states for protection and development of water

fowl habitat. Has provided $226,000 on habitat projects in Utah.

1985-94 Utah Waterfowl Stamp State stamp required to hunt waterfowl for hunters 16 and older. Generated

1.5 million in revenues for the restoration, preservation and development of

waterfowl habitat.

1985, 1990, 1996 Farm Bill Provides incentives and funding to landowners for certain conservation provisions including Wetland Reserve Program, Conservation Reserve Program, Swampbuster, Wildlife Habitat Incentives Program.

1986 North American Waterfowl Coordinated plan between Canada, the U.S. and more recently Mexico to 

Management Plan (NAWMP) protect the continents wetlands and associated wildlife through creation of 

Joint Venture Plans.

1989 North American Wetlands Provides matching funds to State and private wetland protec

Conservation Act (NAWCA) tion activities. Is one of the main funding mechanisms for the NAWMP.

1991 Western Hemispheric Shorebird The GSL was recognized as a Hemispheric Site within the WHSRN. A staReserve Network Designation (WHSRN) tus only achieved by a few important ecosystems supporting shorebirds in 

the Western Hemisphere.

1992 Central Utah Project Completion Act Provided funding for completing CUP water development in Utah. Provided $14 million in mitigation for GSL wetland acquisition, restoration and 

enhancement.

1995 Intermountain West Joint Venture Formally recognized wetland values and established population and habitat 

Plan (IMWJV) goals for the Intermountain Region under the NAWMP.

1998 Great Salt Lake NAWCA Grant Provided $1 million for GSL wetland acquisition, restoration and enhancement under the IMWJV of the NAWMP.
370 Utah Geological Survey

agement techniques was cut short in the early 1980s when

back-to-back 100-year flood events caused a ten-foot (3.048

m) rise in GSL, inundating most managed marsh complexes.

Wetland management on GSL essentially ceased for the large

majority of public and private areas during the mid to late

1980s. Only the areas above flood levels maintained any

kind of water level control which included Salt Creek, most

of the Public Shooting Grounds WMAs, and some of the

higher elevation duck clubs on the Jordan River delta.

Lake levels declined rapidly in the late 1980s and early

1990s. Management activities centered around the awesome

challenge of restoring facilities on over 150,000 acres

(60,705 hm2) of managed marsh that had been developed

through nearly a century of work, but destroyed in just a few

short years. Restoration of state marshes and many private

clubs essentially “chased” the receding lake shore, gambling

that levels would continue to drop. By 1998, essentially all

of the state areas and private clubs were restored and fully

functional. Restoration activities on state management areas

were funded largely through revenues of the Utah Duck

Stamp program, grants from the Federal Emergency Management Agency, and Central Utah Project Completion Act

of 1992 agreements. Restoration at BRMBR began in 1989,

but remains incomplete as of this time. 

Although the great flood of the 1980s had an enormous

impact on wetland vegetation and dependent wildlife, there

were some moderating management consequences. Rebuilding activities allowed new, and more efficient, design features to be incorporated into restoration efforts. The

BRMBR in particular, included a water bypass system and

subdivided many larger management units to enhance water

control. Flooding also provided opportunities to acquire

important adjacent land and water from willing sellers whose

adjacent property was damaged by high water. The Nature

Conservancy acquired areas in the Layton/Kaysville marsh.

Expansions occurred on nearly all state areas during this

period, including the 1,655 acre (670 hm2) Weber Delta Unit

at Ogden Bay WMA and the 1,200 acre (486 hm2) Rainbow

Unit of Harold Crane WMA. Wetland productivity ultimately was enhanced by flood-induced conversion of decadent

and relatively low-productivity marsh to younger, more productive plant communities.

Management Challenges And Sustainable

Resource Needs

Waterfowl

During the 20th century, an incredible amount of knowledge was gained about GSL biological resources through

monitoring, exploration, and experimentation. Much of this

information will help guide management strategies and

preservation activities necessary to sustain migratory bird

abundance and distribution during the new millennium.

However, key management challenges in GSL basin remain,

and for waterfowl, they include effective means of dealing

with predators, disease, undesirable plant communities, and

water needs.

Increasing impacts of predators on waterfowl populations have been well documented across North America. In

GSL, predator abundance and impact appears to be increasing as well. Studies at BRMBR (Williams and Marshall,

1938), Ogden Bay (Nelson,1954) and Salt Creek (Hilliard,1974; Dalton,1976), suggest waterfowl nest success and

abundance was much higher in the first half of the century

than during more recent periods (Huener and Manes,1992a,

b). Recent invasions of red fox, raccoons (Procyon lotor),

apparent increases in other mammalian predators, and colonization of management area dikes by gulls may, in part,

explain the change. Nest success rates reported by Huener

and Manes (1992a, 1992b) were often below levels believed

to be necessary for population maintenance. Future management actions focused on improving reproductive success of

waterfowl, therefore, appear to be warranted to help sustain

local breeding populations.

Waterfowl diseases represent a second mortality factor

with significant consequences to populations in Utah. Disease, directly or indirectly, accounts for the largest proportion of non-hunting deaths in waterfowl (Bellrose, 1976), and

is likely the main cause of death in un-hunted species. Estimated waterfowl losses to botulism on GSL in the summer of

1997 exceeded 500,000 birds, which was nearly twice the

estimated statewide waterfowl harvest that year, and five

times the likely number of ducks fledged on local marshes.

This was one of the most significant botulism mortality

events in the country for the decade. Although stabilization

of marsh impoundments appears to have successfully

reduced the frequency and distribution of severe avian botulism losses over the long term, low-level outbreaks continue

to occur in most years (figure 10), and the potential for catastrophic losses remains. Research on the control of botulism

on GSL has spanned the last 60 years, but new preventative

solutions have yet to be discovered. Picking up carcasses has

historically been and continues to be the main method of

control, but the effectiveness of cleanup during epizootics

has never been proven in large natural settings.

Whereas avian botulism was the major disease impacting waterbirds in the 20th century, avian cholera may be of

equal concern in the next century. Cholera in the U.S. first

appeared in wild birds in 1944, in Texas and California

(Friend, 1987). Today, cholera occurs across North America,

including arctic breeding areas, and losses can rival botulism

in some years. In Utah, cholera made its debut in the fall and

winter of 1994 to 95, when an estimated 30,000 eared grebes

and ducks were lost along the Antelope Island causeway and

Figure 10. Estimated annual waterfowl losses to avian botulism on the

Great Salt Lake, Utah.
Great Salt Lake - An Overview of Change 371

south shore of GSL. In 1998, cholera reappeared killing over

35,000 grebes, gulls, ducks and shorebirds. Considering the

rapid expansion of cholera in the U.S., it is likely that cholera

on GSL will become a significant future management challenge. Although GSL bird populations likely evolved dealing with botulism mortality, cholera represents a new challenge of unknown consequence. 

Control of undesirable plant communities around GSL

will be an ongoing challenge for wetland managers. Most

impounded areas are managed for stable water during spring

and summer to enhance nest success and reduce disease losses of migratory birds. Unfortunately, stable fresh water in

GSL basin also contributes to establishment of dense, and

often monotypic, plant communities. This is particularly true

where water depths are insufficient to prevent plant reproduction and establishment. In general, hemi-marshes (50:50

mix of emergent vegetation and open water) are believed to

harbor the greatest diversity and abundance of birds (Weller

and Spatcher, 1965) and are therefore preferred by area managers. Although management techniques exist to control

plant densities, they are usually intensive, expensive, and

often cannot be applied to broad landscapes.

Some species, including common reed, purple loosestrife (Lythrum salicaria), and tamarisk (Tamarix chinensis)

are rapidly replacing plants with higher values to wildlife.

All three species are hardy competitors and eventually

exclude more desirable plants. In particular, common reed

was among the first plants to colonize disturbed and unvegetated areas after GSL receded in the late 1980s. Efforts to

date to control its spread have only been successful in local,

intensively managed areas. Efforts to develop more costefficient means to deal with undesirable plants will be

required to effectively deal with this problem on a broad

scale. Using biological agents to control some of these plant

species is currently being investigated and shows some promise of success. 

Perhaps the greatest management challenge for protecting habitat and water bird populations on GSL is the procurement of adequate water. Water is needed not only to

meet the needs of managed marshes, but also to supply

unmanaged wetlands that exist below dikes and the myriads

of small creeks and drains that intersect the GSL shoreline.

These needs have long been recognized, but no attempt to

quantify wetland requirements in Utah occurred until studies

were initiated in the 1960s by DWR and Utah State University. Christensen and Low (1970) determined salinity tolerances of several wetland plants and generated a basic water

model to predict water requirements of marshes in northern

Utah. Jensen (1974) used these values to estimate water

requirements of GSL wetlands and demonstrated that over

1.5 million acre-feet of water is annually needed for existing

marshes (table 1). This represents approximately 80 percent

of the 1.9 million acre-feet of surface inflow reaching GSL

each year (Stauffer, 1980). The amount of water currently

held by state, federal and private interests for wetland management has not been compiled, but is undoubtedly much

less than the amount suggested by Jensen. Deficits between

water needs and perfected rights likely exist in most marsh

systems, but is likely greatest on the Jordan River delta,

where approximately half the hunting clubs indicate they

have insufficient rights to meet current and future needs

(Dunstan and Martinson, 1995).

Although identifying water needs is an important step in

securing wetlands, actually obtaining water rights for wetlands is problematic. Currently, Utah water law requires

proof of beneficial use before a right can be perfected. By

legal definition, beneficial use in Utah includes agricultural,

industrial, domestic, and municipal uses. Although some

western states now legally recognize wildlife and recreation

as beneficial uses, Utah does not. The Utah State Water

Engineer does recognize wildlife as a beneficial use by policy, but this could be legally challenged or changed under different administrations. In consideration of this condition,

many private hunting clubs graze cattle, trap muskrats, and

conduct haying operations to secure their water rights.

Additionally, Utah law requires water to be diverted to be put

to beneficial use. Protecting natural wetlands that exist on

undiverted flows or ground water is therefore difficult without constructing dikes and other water management facilities. Future actions to quantify wetland water needs relative

to perfected rights, evaluation of potential upstream depletions of GSL inflows, and development of a long-term comprehensive water plan for GSL wetlands will be needed to

effectively protect GSL wetland resources in the future.

Shore and Colonial Birds

Management challenges for shore and colonial waterbirds, in many cases, do not differ from those of waterfowl.

Similar challenges are coping with predation, disease, and

water needs. Other concerns are the maintenance of shorebird habitats, issues concerning specialty foods such as

halophiles, especially brine flies and brine shrimp, and the

maintenance of fisheries and shallow water. Some of these

concerns also play a role in waterfowl ecology and management. 

Long-term wetland predators, such as the striped skunk

(Mephitis mephitis), weasels (Mustela spp), northern harrier

(Circus cyaneus), American bald eagle (Haliaeetus leucocephalus), peregrine falcon (Falco peregrinus), and California gull have played a role in the predation of shorebird and

colonial waterbirds. Most studies, however, have demonstrated that the most significant wetland predator on the continent is the red fox. Sargeant and others (1984) reported an

estimate of 900,000 adult ducks killed each year for the midcontinental North America. For GSL, the red fox is reported

as the most important predator for snowy plover mortality

(Paton, 1994). The raccoon has established itself as a primary predator on wetland bird nests within the GSL ecosystem. Both the raccoon and red fox are newcomers to GSL

wetlands. These predators were rare in Utah wetlands and

other habitat landscapes before the mid 1970s. In the 1980s,

breeding populations of both predator species were well

established. Currently, efforts through cooperative agreements between management agencies and Utah State University are in place to develop management strategies

focused on preventing red fox and other predation on wetland birds. The BRMBR is experimenting with different

predator exclosure devises to protect breeding wetland

waterbirds (Vicki Roy, USFWS, personal communication,

2000). 

Avian botulism is another cause of significant numbers

of shorebird, gull, and ibis deaths. Records are incomplete,

but subsampling indicates that they may represent 10 or more
372 Utah Geological Survey

percent of waterfowl losses (author’s field notes). There are

at least 30 records of peregrine falcon mortalities or illnesses associated with GSL botulism outbreaks (White, 1963). 

Fowl cholera is responsible for some shorebird and gull

mortality. However, the winter timing of cholera outbreaks,

to date, has precluded affecting most shorebirds due to their

summer and early fall migratory habits. Eared grebes suffer

the greatest loss from cholera as their numbers peak in winter when the disease is active. An outbreak of New Castle’s

disease in double-crested cormorant colonies of the BRMBR

took place during the summers of 1997 through 1999, with

significant loss of young (personal communication, Vicki

Roy). The treatment and protocol for dealing with these, and

other avian disease threats, is carried out by an interagency

Disease Response Team. There is no shortage of opportunities to respond in large, rich, playa lake systems like GSL

because of the immense concentration of waterbirds that

often peak at periods favorable for major epizootics.

Water needs for shore and colonial waterbirds often are

similar to those for waterfowl, but there are some exceptions.

How water lies on the land, the iteration frequency at which

it enters GSL, its abundance, salinity and depth are critical

characteristics that dictate its value to shorebirds. Shorebirds

require a variety of water patterns. For nesting, they often

show preference for water that is nearby or surrounds the

nesting substrate. For brood care, they require fresh water

for drinking and shallow water with rich invertebrate

resources for food. A gradient of wet mud to shallow water,

one-half inch deep to seven inches deep, is a key foraging

substrate for most shorebirds at all ages and activities. Shallow, brine fly-rich saltwater is perhaps the key water habitat

to the immense fall migratory shorebird populations of GSL.

The relationship between fresh water wetlands and saltwater

is perhaps the most unique habitat characteristic of GSL.

Colonial and other waterbirds often need water that supports a fishery. This may be WMA impoundments, rivers,

drainage ditches or large open bays like Bear River and the

Willard Spur. The threats to these water conditions come

from many fronts. Human water consumption in the burgeoning Wasatch Front communities is precluding the

amount and distribution of water to wetlands and GSL. GSL

is the terminus of our drainage systems and therefore

receives the total sum of all chemicals that accumulate in

passage through our towns and cities.

There is a constant threat of urban development to shorebirds and wetlands. Upland open-space buffers are converting from pastures to subdivisions. These shrinking openspace habitats are critical to white-faced ibis, Franklin’s

gulls, long-billed curlews, and Canada geese. On the lakeside there are discussions of inter-island diking, and attempts

at lake stabilization which threaten the very pulse of the lake.

As described elsewhere in detail, the transitory shoreline

allows for habitat dynamics which provide critical shoreline

changes for shorebirds, waterfowl, and colonial birds. Many

irrigation companies are exploring the possibilities of converting from agricultural irrigation to pressurized water systems as the landscape changes from farms to housing. 

Separation of the lake’s brines with extensive dike systems has dramatically affected lake limnology and ecology

(Jehl, 1994; Gwynn,1980). The consequences have played a

profound role in the distribution and abundance of brine

shrimp and brine flies around the lake. These keystone

species, in turn, drive the occurrence and abundance of many

waterbird species using the lake. Currently, the most viable

lake regions for these macroinvertebrates and birds are Farmington Bay and Gilbert Bay. Any future diking that threatens

to modify these brines needs serious contemplation. The

consequences of changing brine densities through diking, or

other developments, could seriously threaten the ecosystem

and brine shrimp industry. Conversely, changes to the Bear

River Bay fishery could threaten the conservation of one of

North America’s most stable, and important, white pelican

colonies, as well as affect significant populations of breeding

double-crested cormorants, western and Clark’s grebes,

Caspian, Forster’s and black terns, and several species of

herons and egrets.

CONCLUSIONS

Joseph R. Jehl, Jr., noted ornithologist of salt lake systems, when referring to GSL said, “The Great Salt Lake is

ornithologically the most impressive salt lake on the continent.” (Jehl, 1994). Lewis W. Oring and Larry Neel, authors

of the Intermountain West Regional Report to the U.S.

Shorebird Conservation Plan said, “The Great Salt Lake

stands out as probably the most important inland shorebird

site in North America ...”. (Oring and Neel,1999)

GSL is recognized regionally, nationally and hemispherically as a wildlife habitat of significance. Many Utah citizens are learning that they virtually live near “something

great” as is indicated in the title of an audio visual presentation by the Friends of the Great Salt Lake. Biological and

ecological investigations continue to support these claims.

Proper public and private stewardship of this richly diverse

and abundant avian habitat will be the key to long-term sustainability.

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