### ABSTRACT

Great Salt Lake is recognized regionally, nationally, andhemispherically 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 managementactivities 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 integratedmanagement 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 birdresources 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 enumeratemigratory bird resources, but to convey the significant ecological role GSL plays in North American and hemisphericbird 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 Much of the information provided is derived from recent unpublished Utah Division of Wildlife Resources surveys, but we also include general summaries from other authors where we felt a historical perspective is important to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 mi 2 (7,800 km 2 ), 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. 

# A VIAN 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.net344 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 theAmericas. In this setting, productive sites for feeding, fattening, and molting of large numbers of migratory birds areisolated 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 W ilson’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 otherwildlife; 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 associatedhalophiles, 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 waterand 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 standthe 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.

W

ithin 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 areother 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 PromontoryMountains. 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) abovesea 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. Althoughthe 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 GSLis 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 supportssome 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 tothe 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 4,200345 Great Salt Lake - An Overview of Change

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/m 2 (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 ofthe 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. Thesouth shore of GSL and Stansbury Island are the main geographic features forming the south arm’s southernboundary. 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 Mountainson 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 hypersalinesystem 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 theseseasons 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 bythe 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. W etlands

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 formallyrecognized in numerous local, international, and hemispheric planning and management efforts. In spite of the long-standing acknowledgment of GSL wetland importance, quantification and classification ofthese wetland resources are imperfect. Jensen (1974) summarized Utah wetland resources based on criteria reflectingtheir 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, aspart 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 sedimentsand 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 hm 3 ). From this, surface water flow, precipitation, and groundwater discharge account for 65 percent, 28 percent and 8 percent, respectively, of totalfresh water inflow. Of the surface flow, the Bear River supplies the greatest amount of water (55 percent), followed bythe Weber River (23 percent) and the Jordan River (14 percent). Ungaged flows from sewage plants and other smalltributaries 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 relievedby 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.

T

able 1. W etland 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

T

ooele 1,440 — 7,640 9,080 48,657

W

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

T

otal 340,043 64,651 69,445 474,139 1,543,860springs. 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 tolong-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 hm 2 ) (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-Julyand 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 hm 2 ) lake-wide, and approximately 17,500 acres (7,083 hm 2 ) 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 and4,200 feet (1,278.6 and 1,280.2 m). Winter and spring increases in GSL elevations therefore result in inundation oftens of thousands of acres with brine in most years, and hundreds of thousands of acres in exceptionally wet years.

W

ind-driven seiches also have dramatic impacts on GSLelevations. “The magnitude of the setup on the speed, direction, fetch, depth of lake at that point, and direction of the 347 Great Salt Lake - An Overview of Change

T

able 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

A

verage 15,977 27,936 17,498 43,914348 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 canerode shorelines and greatly disrupt sediments. As a consequence, seed germination and plant establishment along lake boundaries can be hindered and, in some cases, prevented byfrequent 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 andcompetitive 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 ( T

ypha 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.

W

etlands 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 GSLbasin. 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 orsparsely 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.

W

aste 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 bywater 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 (0.5349 Great Salt Lake - An Overview of Change

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 nestingspecies, 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 ( T axidea 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 othermanmade 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

W aterfowl

W

aterfowl, for the purpose of this discussion, includeducks, 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 areknown 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 GSLelevations. 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.

W

aterfowl 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 GSLoccurs 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

T

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

Species Breeding Migration Wintering

T

undra Swan N C C

T

rumpeter 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

W

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

ythya

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 (A

ythya valisineria ). Mergansers and sea ducks, including bufflehead ( Bucephala albeola ), goldeneye, and scaup (Aythya affinis ), are the last to arrive in November. Cinnamonteal 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), thisnumber does not include populations of birds on many unsurveyed public and private lands. It also does not account forpopulation turnover during the migration period and movement of waterfowl off surveyed areas in response to huntingseasons. 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 arefree 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.

W

aterfowl 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 areafor 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 areasin the central valley of California. Swans stage for a substantial time in marshes of GSL before moving on. Peak fallpopulations 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 tundraswans 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, butinformation 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 percentof 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 nestingareas. 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 ofGSL’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.

W

aterfowl 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 secretiveduring 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 km 2 ) 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 ha 2 ) (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 breedingducks 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 surveysare 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 assumingthere 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 varyfrom 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 substantialpredation 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 ha 2 ), 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 theentire GSL system, they nevertheless are useful in demonstrating the potential and realized production from GSL. 351 Great Salt Lake - An Overview of Change

Figure 4. Densities of ducks counted during May aerial surveys on the Great Salt lake by the Utah Division of Wildlife Resources. T able 4. Estimated breeding ducks on the Great Salt Lake based on aerial transects conducted by the utah Division of
W

ildlife 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

T

otal 231,068

Note: Indicated breeding birds determined from aerial transects

V

isibility correction based on DWR studies in the 1980s Expansion factor = Acres of 1st and 2nd magnitude marsh /aerial

transect acreageThe 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 redheadsfollow 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-qualityfoods. 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.

W

aterfowl 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-breedinggeese (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 tomolt in higher latitudes is also believed to reduce competition for food with successful breeders and their young, aswell 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 breedingperiod. 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 normalbasic metabolic needs. The complete wing molt is particularly taxing on protein resources due to the need for replac352 Utah Geological Survey

T

able 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

Y

ear 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%

A

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

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 denseemergent 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 areain 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 andearly 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

W

aterfowl 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. Becausemigration 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 Pacificflyway (table 7). The Pacific flyway is a waterfowl migraT

able 6. Use of major molting area by the Rocky Mountain Population of Canada geese in the Intemountain West. (from unpublished UDWR data files).

W

yoming Montana Utah

Y

ear 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

A

verage 7,302 4,451 692 7,651 1,128 4,820 1,453354 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 whereflowing 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 existsregarding 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 ontheir 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, orutilize 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

W

est is frequented more often by species of large shorebirdsduring 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 pathwaysthrough 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 representationas 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 PointReyes 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 andalong 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 and1995 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 10and 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 T

able 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 A VERAGE 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%355 Great Salt Lake - An Overview of Change

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 andforaging 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 for340,000 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. T

able 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

W

estern 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.

W

etlands 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. T able 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+

Y

ellowlegs spp. 177 215
Solitary sandpiper 3 0

W

illet 152 35+
Spotted sandpiper 37 7
Long-billed curlew 2 8+
Marbled godwit 16,315 10,979

W

estern 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

W

ilson's phalarope 748 13,692+
Red-necked phalarope 119 0
Phalarope spp. 65,195 35,725
Shorebird spp. 69 0

T

otal 435,810 340,162356 Utah Geological Survey

The BRMBR possesses the largest maintained databasethat includes shorebird numbers for a portion of the ecosystem. They have records spanning several decades; compileddata 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 topresent 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. Ina 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 othershorebirds 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 beenrecorded in field notes of researchers as an ancillary addendum to their specific research projects. Paton and Edwards (unpublished data), have compiled extensive field notes onshorebirds 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 thatthere 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, makingthe 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 ofGSL shorebirds along maintained travel routes, mostly within associated wetlands found on the northeast and northern parts of the lake. Certain methods used in Fellows’ studyproved 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 speciespopulations 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 acadre 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 thesurvey 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 numberreflects 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 largedifference 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 speciescomposition 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 Preserveand 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

r eceded from decaying stands of wetland emergent vegetation.

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

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 standout as important examples of the ecosystem resources, especially when regarding the relationship between salt andfreshwater 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, twooccur 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. Toqualify as a site of hemispheric importance, the area in question must host at least 500,000 shorebirds or 30 percent of aflyway 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 aterritory, 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 issimiliar 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 lakesof Bolivia, central Argentina, and other suitable saline environments. In North America in the spring, they return toGSL 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).

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able 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

Y

ear 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 Aerial358 Utah Geological Survey

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ilson’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 andbrine 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 shallowshorelines, 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 perlinear 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 northarm 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 toreversed 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 morepelagic 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 accessiblenourishment. 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 largerthan 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 fromtheir wintering grounds, mostly from coastal areas in California, Texas, and western Mexico - for example, Marismas Nacionales in Nayarit (Morrison and others, 1994; Shufordand 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

T

able 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 dat a).

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eight, 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% pupae359 Great Salt Lake - An Overview of Change

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 upondense populations of brine flies. These foraging areas are situated in open water with depthsaround 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 theLinking Communities, Wetlands, and Migratory Birds Project. This project was initiated by

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etlands for the Americas of Ottawa, Canada, and by the Western Hemispheric Shorebird

Reserve Network of the Manomet Center forConservation 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 theUnited 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 connectsthese 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 forageand 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

r ecorded 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. Snowyplovers 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 of1988, the DWR organized surveys to gather baseline information on plover distribution for the GSL ecosystem (Halpin and Paul, 1989). These surveys produced counts for 1988and 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 arelaid 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 oftransients; and 3) nesting sites and foraging sites for breeding adults are separate and distinct. Some plovers have beenobserved 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 hisresearch began, yet he found significant breeding and foraging activity in these ephemeral habitats. Impacts of red fox ( V ulpes vulpes ) on snowy plovers andother 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 largestpopulation in the Americas, is the maintenance of undisturbed shoreline that is allowed to fluctuate through seasonsand 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.

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wo important areas for snowy plovers, Lee Creek and Salt

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ells 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 wehave 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 ( T

ringa melanoleuca ), lesser yellowlegs ( T ringa 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 populationknown 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 studiespertaining 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,361 Great Salt Lake - An Overview of Change

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 ofthe 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 ofshore, 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 lakeshoreline 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 T

able 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 T

able 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

V

egetation

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 tern362 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, mayhave 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 oneenormous 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 havenduring 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 managedto 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 bedevastating 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-burntvegetation 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 saltwaterinundated 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 immenseemergent 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 plainof 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 bulrushstems 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 emergentmarshes 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.

W

ithin 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 lakehad 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 bullrushdominant) 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 4,211feet (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 (BridgerlandAudubon 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 363 Great Salt Lake - An Overview of Change

Photo 7. White-faced Ibis provides shade for young nestlings. Figure 6. T otal 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 outtheir 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 theGulf 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; in1996 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 whereoptimal conditions exist for wave and wind abatement to prevent disturbance to their nests. Subsequently, there are earedgrebes 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 ofthe 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 1998.365 Great Salt Lake - An Overview of Change

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 sustainthese 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 (46.82standard 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 notselected 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.

Y

ears of fall GSL grebe surveys have demonstrated that this species keys in on areas of the lake with high densitiesof 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 (FamilyLarinae) 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 structuresas 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 islandcomplex 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. Astudy 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 ofnearby early spring food resources necessary for the production of additional eggs. Mono Lake sits at a higher elevationnear the Sierra Nevada range, and has a paucity of humanprovided food resources available to gulls. Aside from the man-induced values, GSL resources arestill 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 onGSL’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 brineflies in the same, or nearby, locale to reduce energy expenditure in flight travel associated with food gathering. Duringsummer 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 withmasses 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 ofa 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 breeding366 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) EggIsland, 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 the1880s (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 GSLecosystem pelicans (Flannery, 1988; Paul and others, unpublished data). Carp thrive in nutrient-rich shallow-water systems of the waterfowl management areas and freshwaterbays, 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 ofthe 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 likelyfactors 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 youngbanded 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 toGSL, to the Salton Sea, California, and finally reached Colima State, Mexico by the following December. Seven weeksafter 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 itto 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 thisnesting 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).367 Great Salt Lake - An Overview of Change

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 ofibis 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 CarsonLake, 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 beenidentified 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, whichare 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 asurbanization 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 isknown 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 locationthrough time even when the site is flooded or desiccated periodically. Judgements of a nest’s site value must always bemade 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 protectwaterfowl habitat. The Jordan Fur and Reclamation Company was likely the first hunting club organized upon statehood in 1896, hence its commonly used name “Newstate.” Otherprominent 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 smallerstreams 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 hm 2 ) of land is incorporated in private hunting clubs on GSL. The state initiated its first acquisition and managementof 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 hm 2 ) 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 ofwildlife 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 hm 2 ) 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 hm 2 ) 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 hm 2 ) 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 actprovided 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 hm 2 ) sanctuary (located within the Layton-Kaysville Marsh), initiated in 1983, and the National Audubon’s 1,400 acre (567 hm 2 ) 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 hm 2 ), $12 million dollar Salt Lake International Airport Wetland Mitigation area, and the 3,800 acre (1,538

hm 2 ) Inland Sea Shorebird Reserve established by Kennecott Utah Copper. Ducks Unlimited has been active in habitat conservation throughout most of the 20th century, and beganfunding 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 hm 2 ) 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 Gr eat 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 Ti mpie Springs WMA369 Great Salt Lake - An Overview of Change

significant and key component of management throughout the 20th century on GSL, development and manipulation of those same lands share an equally important and informativehistory. 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 LakeBonneville, and too salty to support most plant species. Historical accounts suggest the marshes supported myriads of waterbirds, but were also plagued with enormous diseaselosses 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 breedingbirds 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-desirableplants. 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 andsalinity tolerances of plants as well as management techniques useful in controlling plant succession. Initiation ofadditional research and implementation of successful manT

able 14. Some major conservation actions affecting migratory bird populations on the Great Salt Lake during the 20th century.

Y

ear 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.

W

etland 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 hm 2 ) 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 DuckStamp 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, therewere 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 hm 2 ) Weber Delta Unit at Ogden Bay WMA and the 1,200 acre (486 hm 2 ) RainbowUnit of Harold Crane WMA. Wetland productivity ultimately was enhanced by flood-induced conversion of decadentand relatively low-productivity marsh to younger, more productive plant communities.



### Management Challenges And Sustainable

Resource Needs

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aterfowl

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. InGSL, 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 believedto 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.

W

aterfowl diseases represent a second mortality factorwith significant consequences to populations in Utah. Disease, directly or indirectly, accounts for the largest proportion of non-hunting deaths in waterfowl (Bellrose, 1976), andis 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 successfullyreduced the frequency and distribution of severe avian botulism losses over the long term, low-level outbreaks continueto 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.371 Great Salt Lake - An Overview of Change

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 choleraon 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 truewhere 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 (Wellerand 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 ( L ythrum salicaria ), and tamarisk ( T amarix 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 reedwas 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 plantspecies 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 studieswere 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 currentlyheld 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 insecuring 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 WaterEngineer 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 onundiverted flows or ground water is therefore difficult without constructing dikes and other water management facilities. Future actions to quantify wetland water needs relativeto 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 theseconcerns 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 andcolonial waterbirds. Most studies, however, have demonstrated that the most significant wetland predator on the continent is the red fox. Sargeant and others (1984) reported anestimate 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 wellestablished. Currently, efforts through cooperative agreements between management agencies and Utah State University are in place to develop management strategiesfocused 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).

A

vian 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 more372 Utah Geological Survey

percent of waterfowl losses (author’s field notes). There areat 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 sufferthe 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 interagencyDisease 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.

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ater 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 foragingsubstrate 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

W

illard Spur. The threats to these water conditions comefrom 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’sgulls, 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. Manyirrigation 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 viablelake 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 isornithologically 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 “somethinggreat” 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 diverseand abundant avian habitat will be the key to long-term sustainability.



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