SEABIRD AND MARINE MAMMAL MONITORING 

AND RESPONSE TO A FIREWORKS DISPLAY 

AT GUALALA POINT ISLAND,

SONOMA COUNTY, CALIFORNIA, 

MAY TO AUGUST 2007 

James F. Weigand and Gerard J. McChesney 

United States Department of the Interior 

Bureau of Land Management 

California State Office, Sacramento, CA 

and 

United States Department of the Interior 

Fish and Wildlife Service 

San Francisco Bay National Wildlife Refuge Complex, Newark, CA 

12 February 2008 

SEABIRD AND MARINE MAMMAL MONITORING 

AND RESPONSE TO A FIREWORKS DISPLAY 

AT GUALALA POINT ISLAND,

SONOMA COUNTY, CALIFORNIA, 

MAY TO AUGUST 2007 

James F. Weigand1 and Gerard J. McChesney2 

1

United States Department of the Interior 

Bureau of Land Management 

California State Office, Sacramento, CA 

and 

2

United States Department of the Interior 

Fish and Wildlife Service 

San Francisco Bay National Wildlife Refuge Complex, Newark, CA 

12 February 2008 
Suggested Citation: Weigand, JF; and McChesney, GJ. 2008. Seabird and marine mammal monitoring and 

response to a fireworks display at Gualala Point Island, California, Sonoma County, May to August 2007. 

Unpublished report, USDI Bureau of Land Management, California State Office, Sacramento, CA; and USDI 

Fish and Wildlife Service, San Francisco Bay National Wildlife Refuge Complex, Newark, CA. 38 pp 

Title Page Photo: Marge Anthony 
EXECUTIVE SUMMARY 

During part of the 2007 breeding season, seabirds and pinnipeds were monitored on Gualala 

Point Island, Sonoma County, California. Monitoring was conducted in response to reports 

of disturbance from a fireworks display in July 2006 to nesting seabirds on the island, a part 

of the California Coastal National Monument (CCNM) administered by the United States 

Department of Interior (USDI) Bureau of Land Management (BLM). In 2007, monitoring 

examined potential impacts to seabirds and marine mammals during a fireworks display on 6 

July and gained additional basic knowledge of this little studied colony. The fireworks 

display took place on the north side of the Gualala River mouth in the unincorporated 

community of Gualala, located at the southern end of Mendocino County, California, and 1.8 

km northeast of Gualala Point Island. 

The study period extended from 30 May to 30 August, with a core monitoring period from 1 

to 12 July. The BLM developed monitoring protocols in collaboration with four of its formal 

partners: the California Department of Fish and Game, a CCNM Core-Managing Partner; US 

Fish and Wildlife Service (USFWS) and PRBO Conservation Science, both CCNM 

Collaborative Partners; and its local CCNM Steward, The Sea Ranch Association. BLM and 

USFWS staff biologists and trained volunteers from The Sea Ranch CCNM Stewardship 

Task Force staff carried out protocol monitoring. Monitoring focused on populations of 

breeding seabirds on Gualala Point Island, particularly the Brandt’s Cormorant 

(Phalacrocorax penicillatus), to examine potential responses and effects on reproductive 

success from the fireworks display. Monitoring also included Harbor Seals (Phoca vitulina), 

which haul out on Gualala Point Island. Seabird monitoring consisted of modified versions 

of existing protocols from the USFWS for monitoring seabird colonies from mainland 

vantage points in central California and for aerial photography. Protocols for disturbance 

monitoring were developed from protocols by PRBO Conservation Science, USFWS, and 

other sources. Surveys included four daily bird counts of all species and monitoring of 

visible nests of Brandt’s Cormorants, Pelagic Cormorants (P. pelagicus), Western Gulls 

(Larus occidentalis), and Black Oystercatchers (Haematopus bachmanni) between 1 and 12 

July, with follow-up surveys conducted through 18 July. Aerial photographic surveys of the 

Gualala Point Island Brandt’s Cormorant colony were conducted on six dates between 30 

May and 30 August to document numbers of nests and relative nest success for the entire 

colony. Harbor Seals were monitored following the protocol established by the Point Reyes 

National Seashore. At the same time and location each day, photographs of the visible 

surface of Gualala Point Island were taken to document seabird distribution, densities and 

behavior. Nighttime photography (with digiscoped and infra-red photographs) was 

conducted on two nights, 4 July and 6 July, to examine differences in Brandt’s Cormorant 

behavior prior to and during the fireworks display. Video cameras recorded fireworks 

explosions and the response vocalizations of seabirds. 

Observations documented a visible response by nesting seabirds on Gualala Point Island. 

Digiscoped and infra-red photography during the 6 July fireworks display showed that 

Brandt’s Cormorants quickly changed from resting to erect postures at the first fireworks, 

followed by birds moving about or departing from the island. Western Gulls also flushed, 

circled and called during the fireworks display. During the study period, 90 Brandt’s 

Cormorant nests were documented on Gualala Point Island. Of these, seven nests (35% of 
nest failures) were abandoned in the two days between 5 and 7 July, and another seven nests 

were abandoned between 7 and 12 July. These losses contrast with the abandonment of only 

six nests (30% of nest failures) for the 30-day period from 5 June to 5 July. Two of nine 

nests monitored from the adjacent mainland were abandoned between 6 and 8 July. The high 

rate of Brandt’s Cormorant nest abandonment between 5 and 7 July, and possibly nest 

abandonment from 7 to 12 July, likely resulted from fireworks disturbance. 

Pelagic Cormorants abandoned both of the two monitored nests on Gualala Point Island 

between 10 and 16 July for unknown reasons. For one day after the fireworks display, counts 

of adult Western Gulls on the island declined significantly, but no Western Gull nesting 

failures were known to have occurred during the count period. California Brown Pelicans 

(Pelecanus occidentalis californicus) did not use Gualala Point Island as an overnight roost 

until after the date of the fireworks display. Other seabird species were too few in number or 

too difficult to monitor to detect potential responses from the fireworks display. No 

significant response was detected for Harbor Seals, which were not present on the island 

during the fireworks display. 

Other human and “natural” disturbances to the island’s wildlife were rare and minor, with no 

detectable impacts to nesting birds or pinnipeds. 

ii 
ACKNOWLEDGMENTS 

The authors gratefully acknowledge the assistance of The Sea Ranch CCNM Stewardship 

Task Force, in particular: 

CONNIE SCHIMBOR and DIANE HICHWA for organizing and shepherding 

equipment, data sheets, and volunteers to needed locations; 

BRYANT HICHWA, ROZANNE RAPOZO, and CRAIG TOOLEY for planning and 

undertaking nighttime, daytime, and aerial photography; 

JERRY RENCH for his piloting skills to expand the aerial inventories; 

SANDRA BUSH and BONNIE PLAKOS for Harbor Seal monitoring; 

RITA PECK and PHYLLIS SCHMITT for video and sound recording; 

GEORGE BUSH for acoustic instrumentation and monitoring; 

ROZANNE RAPOZO and JULIE GIBSON for data entry and proofing, and database

management; 

MICHAEL LANE for valuable insights into the unique geology of Gualala Point 

Island and its bearing on seabird habitat and donated his GIS and mapping 

services; 

RICHARD KUEHN for document research and historical background on seabird 

behavior in the area based on years of daily observations; and 

RICHARD SCHIMBOR and DEAN SCHULER assisted in all manner of logistics. 

The following people donated their time and skills to assist with seabird monitoring: 

GINGER ALEXANDER DOROTHY GREGOR

THOMAS ALEXANDER KENNETH HOLMES

GEORGE ANDERSON MARY HUNTER

MARGE ANTHONY LINDA KEIR

SUSAN BECHTEL LEE KOSSO

ELIZABETH BURRIDGE ELAINE MAHAFFEY

PAULINE DAKIN GEORGE MARSHALL

JAMIE EDWARDS MICHELE MARSHALL

JEANNE GADOL GRACE STEURER

STEVEN GADOL JAMES TACKETT

MEL GERST JULIE VERRAN

BARBARA GOMES

In addition, field work and photographic analysis accomplished for this study could not 

have happened without the assistance of BLM wildlife biologists, PAUL ROUSH and 

GARY DIRIDONI. HERRICK HANKS, manager of the BLM California Coastal National 

Monument, and JOHN FOX, Community Manager of The Sea Ranch Association, 

provided funding, logistical support, and public relations efficiently and capably to 

support this effort. The authors also thank PHILLIP CAPITOLO and DEASY LONTOH of 

Humboldt State University and WAYNE BURNETT of the California Department of Fish 

and Game for assistance on aerial photographic surveys. 

This report benefited greatly from thoughtful reviews by PAUL ROUSH and PETER 

WARZYBOK. 

iii 
TABLE OF CONTENTS 

Introduction............................................................................................................................1 

Methods..................................................................................................................................1 

Results....................................................................................................................................5 

Discussion..............................................................................................................................23 

Literature Cited ......................................................................................................................26 

Appendices 

Appendix 1 Histories of Brandt’s Cormorant Nest and Territorial Sites Recorded in 

Aerial Photographs, Gualala Point Island, 30 May to 12 July 2007...........29 

Appendix 2 Bird Census Totals by Species, Vantage Point and Time of Day, 

1 to 12 July 2007...................................................................32 

iv 
LIST OF TABLES 

Table 1 Summary of the status of Brandt’s Cormorant nest and territorial sites as 

determined from aerial photographs, Gualala Point Island, 30 May to 

12 July 2007...................................................................................................7 

Table 2 Comparison of nest counts for breeding seabirds on Gualala Point Island in 

1989 and 2007................................................................................................17 

Table 3 Summary of daily status for the nine Brandt’s Cormorants nests monitored 

from the mainland on Gualala Point Island, 1-18 July 2007 .........................18 

Table 4 Summary of daytime disturbances to seabirds on Gualala Point Island 

recorded during seabird counts and nest surveys, 1-12 July 2007.................21 

LIST OF FIGURES 

Figure 1 Map of Gualala Point Island and vicinity, Mendocino and Sonoma counties, 

California .......................................................................................................2 

Figure 2 Aerial photograph of Gualala Point Island from the southeast, 30 May 2007. 

The arrow points to the Brandt’s Cormorant colony, indicated by the dark 

mass of nests and birds surrounded by white guano......................................7 

Figure 3 Time series of aerial photographs of the Brandt’s Cormorant colony on 

Gualala Point Island, 30 May to 30 August 2007. Site numbers used for 

monitoring are indicated in each photograph.................................................8 

Figure 4 The Brandt’s Cormorant colony on Gualala Point Island, photographed from 

the south vantage point at mid-morning on 6, 7, 10 and 12 July 2007..........13 

Figure 5 Location of the Black Oystercatcher nest site, marked in red, from the 

north vantage point, Gualala Point Island, July 2007 ....................................14 

Figure 6 View of the Western Gull colony on Gualala Point Island from the south 

vantage point at 10:30 h on 6 (upper photo) and 7 (lower photo) July 2007. 

Note the higher density roost near the top of the island on 6 July that was 

absent throughout the day on 7 July. .............................................................15 

Figure 7 Pigeon Guillemot nest crevices on Gualala Point Island, marked in red, 

detected as of 5 July 2007 from the south (upper photo) and north (lower 

photo) vantage points.....................................................................................16 

Figure 8 Images of the two Pelagic Cormorant nest sites on Gualala Point Island from 

three different dates, 1 to 12 July 2007..........................................................19 

v 
Figure 9 Census of Harbor Seals at daytime low tide, Gualala Point Island, 1 to 12 July 

2007................................................................................................................21

vi 
INTRODUCTION 

Understanding impacts from human disturbances to seabird colonies may be key to restoring 

certain nesting seabird populations along the California coast. Disturbances to seabirds 

during their reproductive cycles are a critical element for analysis in the process of adapting 

management to preserve and augment California seabird populations. Sources of human 

disturbance that are well recognized include habitat destruction, close-approaching boats, 

humans on foot and low-flying aircraft (e.g., McChesney 1997, Carney and Sydeman 2003, 

Rojek et al. 2007). Another source of human disturbance to seabirds that is not well 

documented is the display of celebratory fireworks. In California, only one study (Wengert 

and Gabriel 2002) of the heron colonies of Humboldt Bay has previously looked at the 

impact of fireworks on colonial waterbirds in California. 

This monitoring study was conducted to determine how a recently initiated Independence 

Day fireworks display affected nesting and resting seabirds and marine mammals on Gualala 

Point Island within the California Coastal National Monument (CCNM), administered by the 

US Department of the Interior (USDI), Bureau of Land Management (BLM). Concern about 

potential impacts to nesting seabirds originated from observer reports of large numbers of 

birds on Gualala Point Island that flushed and flew into the darkness above the island on 2 

July 2006 during the First Annual Gualala Festivals Committee Independence Day fireworks 

display. 

The BLM and its partner regulatory wildlife agencies, the California Department of Fish and 

Game, the US Fish and Wildlife Service (USFWS), and the National Oceanic and 

Atmospheric Administration’s National Marine Fisheries Service, wanted to assess whether 

the Gualala fireworks display impacted breeding success or attendance patterns of seabirds 

and marine mammals at Gualala Point Island and to learn the current status of the island’s 

natural resources. To obtain information, BLM and USFWS biologists worked with The Sea 

Ranch CCNM Stewardship Task Force (hereafter “the Task Force”) to monitor seabirds and 

marine mammals on Gualala Point Island before, during, and after the fireworks display 

using a combination of aerial and land-based techniques. This report summarizes the study 

results from 2007. 

METHODS 

Study Area 

Gualala Point Island (California Seabird Colony Number SO-384-01; 38o45’04” N, 

123o31’42” W) is located just offshore at the northern border of Sonoma County, California. 

The island is situated 1.8 km southwest from the Gualala Festivals Committee fireworks 

launch site located on a bluff top above the mouth of the Gualala River in the unincorporated 

community of Gualala, Mendocino County (Figure 1). 

Geological factors combine to make Gualala Point Island a unique and favorable habitat for 

colonial seabirds. Gualala Point Island is part of the Gualala Block, a narrow crustal sliver 

that extends roughly from Point Arena in Mendocino County south to Fort Ross in Sonoma 

1 
County. The Gualala Block consists predominantly of sedimentary formations deposited 

originally hundreds of miles south of their current location and subsequently transported 

northward along the San Andreas Fault System. The Gualala Block is the most northerly 

large assemblage of rocks on the west side of the San Andreas Fault (M. Lane, pers. comm.). 

Additionally, the large-scale movement has brought to the Gualala area some rocks, such as 

limestones, that are uncommon along the northern California Coast. This small area of wellbedded sedimentary rocks contrasts sharply with the heterogeneous lithologies of the 

Franciscan Group prevalent north of San Francisco. 

Figure 1 – Map of Gualala Point Island and vicinity, Mendocino and Sonoma counties, 

California. 

Gualala Point Island bedrock consists of interbedded shales and massive sandstones of the 

Paleocene-Eocene Germán Rancho Formation. However, at this locality, crustal deformation 

associated with northward transport of the Gualala Block has caused the bedding planes to 

2 
twist and become vertical. The result is a corrugated effect to the rocks, with the softer 

shales eroding more rapidly than the massive resistant sandstones. Crevices that form 

between the interbedded rock layers form nesting sites for Pigeon Guillemots (Cepphus 

columba) and rock ledges create nesting habitat for Pelagic Cormorants (Phalacrocorax 

penicillatus). Brandt’s Cormorants (P. penicillatus) nest primarily on the limestone flats of 

the island. 

Monitoring 

The study period ranged from 30 May and 30 August 2007, with a more intensive monitoring 

period (hereafter referred to as the “count period”) between 1 and 12 July 2007 (six days 

before and six days after the fireworks display). Multiple methods were used to record bird 

and mammal numbers, reproductive success, and potential impacts of fireworks displays and 

other disturbances. These methods included aerial photography, land-based surveys, landbased photography both during the day and at night (including during the fireworks display), 

and audio recordings made during the fireworks display. Data collection (except as indicated 

below) was conducted by BLM staff and Task Force volunteers. Data analysis and 

interpretation was conducted by the authors with assistance from Paul Roush (BLM). 

Documentation of the monitoring protocol used for this study (USDI Bureau of Land 

Management and The Sea Ranch CCNM Stewardship Task Force 2008) is available from the 

BLM California State Office. 

Aerial Photography: The USFWS, in cooperation with Humboldt State University and the 

California Department of Fish and Game, photographed Gualala Point Island on 30 May 

2007 during an annual aerial photographic survey of Common Murre, Brandt’s Cormorant, 

and Double-crested Cormorant colonies in northern and central California. Subsequently, a 

volunteer pilot and a volunteer professional photographer flew additional surveys of Gualala 

Point Island on 5 June, 5, 7, and 12 July, and 30 August, using a protocol comparable to that 

used by the USFWS. A planned flight for 6 July was cancelled because of heavy fog and 

low visibility. Surveys on 30 May were conducted at 210-230 m (700-750 ft) altitude in a 

fixed-wing, high-wing Partenavia aircraft. Photographs were taken through a belly port by 

two photographers with Canon 30D digital cameras and 70-200 mm or 300 mm telephoto 

lenses. All other flights were conducted above 300 m (1000 ft) altitude in a fixed-wing 

Cessna 172-M aircraft and digital photographs were taken through a side window. Survey 

altitudes were flown high enough to alleviate disturbance to seabirds from these types of 

fixed-wing aircraft. Photographs were taken of the entire island, with a focus on the Brandt’s 

Cormorant colony. 

From each aerial survey, the photograph with the highest quality and most complete coverage 

of the cormorant colony primarily was used, augmented by additional photos as needed for 

complete views of all nests. From the photographs, all active nest sites were identified and 

assigned unique site numbers. For each survey, the status of each nest was identified using 

the following codes: 

E = empty nest S = adult sitting on nest 

P = poorly built nest D = adult standing at nest site 

F = fairly well-built nest T = territorial site, i.e., adult bird(s) on 

W= well-built nest territory but no nest 

C = chick(s) visible V = vacant site, i.e., no birds present 

3 
“Active nests” were well-built or fairly well-built nests with either an adult sitting on the nest 

or standing at a nest containing visible eggs or visible chicks, except for nests known to have 

failed recently (i.e., too soon to have laid a new clutch of eggs). “Territorial sites” had one of 

three characteristics: adults standing or sitting at a potential nest site with little or no nesting 

material; adults on a poorly-built nest; or adults sitting or standing at a well-built or fairly 

well-built nest that was visibly empty or known to have failed recently. From these data, a 

history of each nest site was established, including seasonal site status (breeding or 

territorial), approximate breeding phenology, and whether or not the nest failed during the 

survey period. Breeding sites were those with confirmed eggs or chicks or where breeding 

was inferred by nest status. Territorial sites were those where breeding could not be 

confirmed or inferred by nest status. 

Seabird Counts from Mainland Vantage Points: These counts were conducted by BLM 

wildlife biologists and volunteers from the Task Force. Adults and ambulatory chicks of all 

seabirds on Gualala Point Island were counted through 20x to 60x spotting scopes from two 

mainland vantage points four times daily (05:30, 08:30, 10:00 and 13:30 h), visibility 

permitting, during the 1-12 July count period. One vantage point viewed the north side, and 

the other viewed the south side of the island. Observers also recorded any bird and marine 

mammal observations at 21:00 h just before sunset on the evening of 6 July. 

UTM locations in Zone 10N (NAD 1983) of the vantage points are as follows: 

North Vantage Point: 454244 E 4289459 N about 245 m from the island 

South Vantage Point: 454411 E 4289224 N about 305 m from the island 

Seabird Nest Monitoring from Mainland Vantage Points: A modified version of the USFWS 

Common Murre Restoration Project protocol for Brandt’s Cormorant nest monitoring 

(McChesney et al. 2007) was used. Along with Brandt’s Cormorants, the protocol included 

nest monitoring of two other species on Gualala Point Island: Pelagic Cormorant and 

Western Gull (Larus occidentalis). Observations were recorded during the same times that 

seabird counts took place. For each species, visible nests were assigned unique numbers and 

identified on photographs. During the count period, the status of each nest was identified by 

recording the number of adults present, adult posture (sitting or standing), and the number of 

eggs and chicks visible. 

Daytime Marine Mammal Monitoring: The count form for monitoring Harbor Seals (Phoca 

vitulina) at Point Reyes National Seashore and along the Sonoma County coast including The 

Sea Ranch (Manna et al. 2006) was adopted for this project. Censuses of Harbor Seals took 

place at the daytime low tide closest to seabird count times. In addition, as time permitted, 

seals were counted during seabird counts. 

Daytime Disturbance Monitoring: Disturbances to seabirds were recorded systematically. 

The protocol to monitor and characterize disturbances combined pre-established protocols 

from PRBO Conservation Science (unpubl. data), USFWS (McChesney et al. 2007), and 

Jaques and Strong (2002). All aircraft flying below 300 m (1000 ft) and boats approaching 

to within 300 m (1000 ft) of Gualala Point Island were recorded, as well as any visible 

disturbance behaviors to seabirds or seals (e.g., flushing or displacement). 

4 
Daytime Land Photography from Mainland Vantage Points: An initial photographic survey 

of Gualala Point Island was conducted at the onset of the count period. Photographs taken 

with a Canon 20D digital single lens reflex (DSLR) camera with a 300 mm lens and a 2x 

teleconverter (magnification = 12x) documented the initial nest site locations for both 

Western Gulls and Brandt’s Cormorants as well as other species of interest. These 

photographs served as the basis for subsequent monitoring. On most days during the count 

period, one or more observers took photographs of Gualala Point Island from each of the 

mainland vantage points between 10:30 and 11:30 h. 

Nighttime Photo Monitoring: On both 4 and 6 July, two volunteer professional photographers 

took nighttime photographic images of the Brandt’s Cormorant colony on Gualala Point 

Island from the south vantage point. Two digital photographic methods were used: visible 

light digiscoping and infrared photography. On each night, photography documented bird 

activity for 90 minutes after sunset. Images provided for comparison of cormorant activity 

during the same time on the two evenings, one before and one during the fireworks display. 

Nighttime Video and Sound Recording: Continuous video and audio recordings of Gualala 

Point Island were conducted from both mainland vantage points during the fireworks display. 

One observer used a Sony Handycam DCR-DVD308 mounted on a tripod to capture video 

and sound from 21:00 until 22:00 h, and another observer used a Sony 20x optical Handycam 

(DCR-HC26). The time marks on the video corresponded within one minute of the time 

recorded on the nighttime DSLR images. 

Acoustic Monitoring: Sound monitoring took place during the Gualala Festivals Committee’s 

fireworks display. Monitoring consisted of a sound recording of the entire fireworks display 

from the north vantage point for Gualala Point Island and of sound meter readings filmed in 

real time alongside a GPS unit with satellite clock time. One sound level meter, a TenmaTM 

model 72-860, measured sound during the fireworks display. 

RESULTS 

Aerial Photography of the Brandt’s Cormorant Colony 

In 2007, the Brandt’s Cormorant colony was limited to a relatively small area on the 

southwest side of Gualala Point Island (Figure 2). Figure 3 (a-e) shows aerial photographs of 

the entire Gualala Point Island Brandt’s Cormorant colony from six surveys between 30 May 

and 30 August 2007. During the survey period, a total of 93 sites were identified and 

assigned unique site numbers that are indicated in the photos. Histories of each site are 

shown in Appendix 1. A small number of apparent territorial sites that were present on 

single surveys only were not assigned site numbers. 

Of all sites followed, 90 were identified as breeding sites and three as territorial sites (i.e., 

where egg-laying was not likely to have occurred). Most nests (72%) recorded during the 

study period were active when the colony was first photographed on 30 May (Table 1); most 

of these likely had eggs at that time based on well-formed nest structures and adults sitting in 

incubation postures. Nest establishment continued for some time afterward, and by 5 July an 

additional 25 nests were added. By 5 July, part of the colony had entered the chick period, as 

5 
twelve nests had relatively large chicks (ca. two to four weeks old) visible in nests. Six 

nests, or 8.2% of the 5 June total and 6.7% of the seasonal total, failed between 5 June and 5 

July. 

On 7 July, no new nests were recorded and six additional nests had visible chicks. Seven 

nests, or 8.3% of the 5 July nest total and 7.8% of the seasonal total, were newly failed. Of 

these, none had visible chicks (i.e., adults were either incubating eggs or brooding small 

chicks) on 5 July, two were newly established between 5 June and 5 July and one was 

established between 30 May and 5 June. Of fourteen total nests with visible chicks, all were 

attended by adults, and no chicks appeared to be wandering from natal nests. 

On 12 July, another seven nests were newly failed and an additional 28 nests had visible 

chicks. Of failed nests, none had visible chicks in 5 July photographs. Three were 

established by 30 May, two were established between 30 May and 5 June, one was 

established between 5 June and 5 July, and one was established between 30 May and 5 July 

(nest-building on 30 May but no data on 5 June). Some chicks were clearly larger than on 

previous surveys, and some chicks were large enough (ca. minimum three to four weeks old) 

to wander from natal nests. Five sites that failed between 5 and 7 July were attended on 12 

July: three had large chicks present that had wandered from other nearby nests; and two were 

attended by territorial adults only. These sites were considered to be territorial sites and not 

active nests because of their recent failures. Two nests had visible eggs, indicating that some 

pairs were still incubating. 

By 30 August, the entire nesting area was abandoned following the end of breeding. This 

last survey showed that no pairs that failed nesting in July re-nested successfully. Based on 

averages of eight days to lay a new egg, a 30-day incubation period, and about 30 days until 

chicks can become independent from natal nests (Ainley and Boekelheide 1990, Carter and 

Hobson 1988), active nests still would have been present on 30 August if re-nesting after 6 

July had been successful. 

In summary, 20 nests, or 22.2%, of documented nests failed between 5 June and 12 July. Of 

failed nests, 30% failed between 5 June and 5 July and 35% failed during each of the periods 

5-7 July and 7-12 July. Cumulatively, 70% of nest failures occurred during the brief period 

between 5 and 12 July. By 12 July, 46 nests (51%) had visible chicks, with the oldest chicks 

close to 30 days old and wandering from natal nests. Based on those chicks, the earliest eggs 

were laid in mid-May. However, at least some nests clearly still had eggs on 12 July, 

indicating that egg-laying had continued at least through mid-June. No failed nests had 

chicks visible to observers prior to failure, indicating that failed nests had either eggs or very 

small (or young) chicks prior to failing. 

6 
Figure 2 – Aerial photograph of Gualala Point Island from the southeast, 30 May 2007. 

The arrow points to the Brandt’s Cormorant colony, indicated by the dark mass of nests 

and birds surrounded by white guano. 

Photo courtesy of US Fish and Wildlife Service 

Table 1 - Summary of the status of Brandt’s Cormorant nest and territorial sites as 

determined from aerial photographs, Gualala Point Island, 30 May to 12 July 2007. 

Reproductive Stage 30 May 5 June 5 July 7 July 12 July 

Active nests

a 65 83h 84 77 69 

Active territorial sitesb 15 7 4 5 11 

Total active sites 80 90 88 82 80 

Unknownc 0 1 0 0 0 

Newly categorized nest sites 

(former territorial sites)

d 0 10 5 0 0 

New nest sitese 65 8 2 0 0 

Total new nestsf 65 18 7 0 0 

New territorial sites

e 15 3 0 0 0 

Total new sitesg 80 11 2 0 0 

Nests w/newly visible chicks 0 0 12 6 28 

Newly failed nests 0 0 6 7 7 a

 Includes: 1) nests with birds sitting in fairly well-built to well-built nests (probably incubating eggs or

brooding chicks); and 2) nests with visible chicks that were not recorded as failed on a previous survey. b

 Includes nests that failed previously but were attended by adult birds on the survey date. c

 No photo coverage available for site that was active on later surveys only. d

 Sites categorized as nests that were present and categorized as territorial on previous survey(s). e Sites not recorded as either nest or territorial sites on previous surveys. f Sum of “newly categorized nest sites” and “new nest sites.” g

 Sum of “new nest sites” and “new territorial sites.” 

h

 Includes one site (Site 91) with no photo coverage that was known to be active before and after 5 June. 

7
Figure 3 (a through e) – Time series of aerial photographs of the Brandt’s Cormorant 

colony on Gualala Point Island, 30 May to 30 August 2007. Site numbers used for 

monitoring are indicated in each photograph.1 

Photo by Gerard McChesney, US Fish and Wildlife Service 

a) 30 May 2007 

8 
Photo © Craig Tooley, The Sea Ranch School of Photography 

b) 5 June 2007 

Photo © Craig Tooley, The Sea Ranch School of Photography 

c) 5 July 2007 

9
Photo © Craig Tooley, The Sea Ranch School of Photography 

d) 7 July 2007 

Photo © Craig Tooley, The Sea Ranch School of Photography 

e) 12 July 2007 

10
 Photo © Craig Tooley, The Sea Ranch School of Photography 

f) 30 August 2007 

1

For the photographs on 5, 7 and 12 July 2007, nest numbers are color coded as follows: 

blue: active nests or territorial sites; 

red: 6 nests categorized as newly failed on 5 July 2007; 

green: 7 nests categorized as newly failed on 7 July 2007; and 

pink: 7 nests categorized as newly failed on 12 July 2007. 

11
Seabird Counts from Mainland Vantage Points 

Appendix 2 displays graphs of seabird count data by count time and vantage point for the key 

species monitored on Gualala Point Island. All but the Brown Pelican nested on the island. 

Where data bars are absent in graphs, either no birds were present or no data were collected 

because of adverse weather conditions. Foggy conditions on 6-7 July precluded some counts 

and comparisons between the day of the fireworks and the day immediately after the 

fireworks. 

Brown Pelican: Gualala Point Island is frequently a nocturnal roost for Brown Pelicans 

during their post-breeding dispersal. During the count period, many more pelicans were 

observed flying by Gualala Point Island than actually landing on the island, and pelicans 

were absent on the island on most days before the fireworks display. Large numbers of 

pelicans have roosted on Gualala Point Island in past summers, often reaching 100 birds 

before 1 July (R. Kuehn and G. Marshall, pers. comm.). The island did not appear to be a 

significant nocturnal roost site during the count period in 2007. When present during the 

day, most birds roosted on the lower rocks at the west end of Gualala Point Island or 

occasionally on the lower rocks on the east end of the island. 

Brandt’s Cormorant: Only a small portion (10%) of the Brandt’s Cormorant colony was 

visible from the mainland and only from the south vantage point. Brandt’s Cormorants were 

typically most numerous during the two earlier daily count times (see Appendix 2). Between 

1 and 10 July, no consistent trend in counts was discernible, although a decline may have 

occurred between 5 and 9 July. Fog prevented counts at 05:30 and 08:00 h on 6 July, making 

this assessment less clear. On 11 and 12 July, an influx of non-breeding or post-breeding 

Brandt’s Cormorants arrived and began roosting on Gualala Point Island. Their different 

origin was apparent by the presence of immature birds, not previously recorded on the island 

during the count period, and a clear spatial segregation between the roosting birds and the 

nesting colony. 

12 
Figure 4 shows the Brandt’s Cormorant colony on Gualala Point Island from the south 

vantage point on four different days between 6 and 12 July. Nest #1 at the far left edge of the 

colony was found to be abandoned on 8 July and then reoccupied on 12 July. A Common 

Murre appears in flight in the 12 July photograph. 

Figure 4 – The Brandt’s Cormorant colony on Gualala Point Island, photographed from the 

south vantage point at mid-morning on 6, 7, 10 and 12 July 2007. 

Brandt’s Cormorants GPI-S 20070706 Brandt’s Cormorants GPI-S 20070707 

Brandt’s Cormorants GPI-S 200707010 Brandt’s Cormorants GPI-S 20070712 

Photos © Rozanne Rapozo, Nature As I See It 

Pelagic Cormorant: Counts of Pelagic Cormorants on Gualala Point Island consisted mostly 

of non-breeding birds. Most birds congregated on ledges along the north side of the island. 

Bird counts varied considerably between count times and days. No trend in counts was 

evident during the count period. 

13 
Black Oystercatcher: One breeding pair of oystercatchers was located from the north 

vantage point (Figure 5). Parents fed the young throughout the count period after first being 

discovered on 2 July 2007. All three young birds were first seen together on 6 July 2007. 

The chicks were still present at the end of the count period and beyond. 

On most days, the total numbers of adult oystercatchers using Gualala Point Island for 

feeding and resting included more than the breeding pair. Most activity occurred in the 

intertidal foraging zone. They were also regularly seen in transit between the island and the 

mainland. Daily maximum counts ranged from two to seven birds. 

Figure 5 – Location of the Black Oystercatcher nest site, marked in red, from the north 

vantage point, Gualala Point Island, July 2007. 

Photo by Paul Roush, USDI Bureau of Land Management 

Western Gull: Although more Western Gull nests were visible from the north vantage point 

of the island, counts of adult Western Gulls were consistently higher from the south vantage 

point (Appendix 2). Immature Western Gulls were virtually absent from the island during 

the count period, as noted in previous years (R. Kuehn, pers. comm.). Most adult gulls not 

attending nests roosted on the sparsely vegetated flat top of the east end of the island. 

Maximum daily counts usually occurred during the second or third shift (08:00 or 10:30 h). 

Counts of adult Western Gulls generally increased through the count period, except for a 

clear decline that lasted through the day on 7 July (Appendix 2, Figure 6). These counts 

were among the lowest of the count period and indicated that many gulls departed the island 

and remained away during the course of that day. Otherwise, the general increase observed 

suggested an influx of non-breeders or failed breeders from other colonies. 

Figure 6 shows the Western Gull colony as viewed from the south vantage point on 6 and 7 

July at about 10:30 h each day. The higher density gull roost on top of the island on 6 July 

was absent on 7 July. 

14 
Figure 6 – View of the Western Gull colony on Gualala Point Island from the south vantage 

point at 10:30 h on 6 (upper photo) and 7 (lower photo) July 2007. Note the higher density 

roost near the top of the island on 6 July that was absent throughout the day on 7 July. 

Western Gulls GPI-S

 20070706 

Western Gull GPI-S

 20070707 

Photos © Rozanne Rapozo, Nature As I See It 

15 
Pigeon Guillemot: Observers at both the north and south vantage points regularly noted 

Pigeon Guillemots resting on ledges and cliffs as well as entering crevices where birds were 

believed to be nesting (Figure 7). 

Figure 7 - Pigeon Guillemot nest crevices on Gualala Point Island, marked in red, detected as 

of 5 July 2007 from the south (upper photo) and north (lower photo) vantage points. 

Photos by Paul Roush, USDI Bureau of Land Management 

Counts of Pigeon Guillemots may have contained birds simultaneously visible to observers at 

both the north and south vantage points. Highest guillemot counts occurred during the first 

two shifts each day. This pattern was expected because guillemots tend to congregate near 

16 
nest sites in the early morning hours (Carter et al. 1992, Ewins 1993). Numbers of 

guillemots counted generally increased through the count period. 

Other Bird Species Observed: In addition to bird species discussed above, observers recorded 

the following species on Gualala Point Island during the count period: 

Double-crested Cormorant Phalacrocorax auritus 

Unknown Sandpiper Calidris spp. 

Whimbrel Numenius phaeopus 

Ring-billed Gull Larus delawarensis 

Heermann’s Gull Larus heermanni 

Common Murre Uria aalge 

Cliff Swallow Petrochelidon pyrrhonota 

Barn Swallow Hirundo rustica 

European Starling Sturnus vulgaris 

Brewer’s Blackbird Euphagus cyanocephalus 

Common Murres were observed on nine days during the main count period and on 16 to 18 

July, usually among the nesting Brandt’s Cormorants. Counts ranged from one to seven 

birds. Although this abundant California breeder has the closest colonies located just north 

of Point Arena, nesting has not been documented on Gualala Point Island or anywhere else in 

Sonoma County (Carter et al. 2001). 

Seabird Nest Counts 

All species noted as nesting on Gualala Point Island during the last complete colony survey 

in 1989 (Carter et al. 1992) were nesting in 2007 (Table 2). Historically and in 2007, 

Brandt’s Cormorants have been the most numerous nesting seabird species. Although census 

methodologies were different each year except for Brandt’s Cormorants, numbers of 

breeding birds for most species appeared similar between the 1989 and 2007 counts. 

Table 2 – Comparison of nest counts for breeding seabirds on Gualala Point Island in 1989 

and 2007. 

Species 

1989 2007 

Nest 

Count 

Census 

Method 

Census 

Date 

Nest 

Count 

Census 

Method 

Census 

Date 

Brandt’s 

Cormorant 237 aerial survey 23 May 841 aerial survey 5 July 

Pelagic 

Cormorant 2 boat survey 

6 June 2 mainland 

survey 1 July 

Black 

Oystercatcher 

0 boat 

survey 

6 June 1 mainland 

survey 2 July 

Western Gull 13 boat 

survey 

6 June 17 mainland 

survey 5 July 

1

High single survey count. The seasonal total for all nests constructed in 2007 was 90 nests (see text). 

Brandt’s Cormorant nest counts were conducted using aerial photographic surveys. A total 

of 90 Brandt’s Cormorant nests were identified over the five surveys conducted between 30 

17 
May and 12 July 2007, with a high count of 84 nests on 5 July 2007. Only 65 nests were 

active during the standardized annual USFWS survey on 30 May (Table 1). Other past nest 

counts have been: 620 in 1980 (Sowls et al. 1980); 78, 139, and 125 nests in 1993, 1994, and 

1995, respectively (Carter et al. 2000); and 132 in 2003 (Capitolo et al. 2004). 

Thus, nest counts of Brandt’s Cormorants on Gualala Point Island in 2007 were 85% lower 

than the high count in 1980 and 32% lower than the most recent count in 2003. Comparing 

the standardized USFWS survey periods, the 2007 nest count was 51% lower than the 2003 

count. 

Seabird Nest Monitoring 

Brandt’s Cormorant: In 2007, only about 10% of the Brandt’s Cormorant colony was visible 

from the mainland and only from the south vantage point. Although views were not ideal, 

the data obtained were sufficient to establish nesting status during the count period for nine 

sites (Table 3). Of these, six nest sites had breeding confirmed by the presence of chicks. 

Two other sites were not confirmed to have eggs or chicks, but breeding was inferred by the 

conditions of the nests and adult behavior (i.e., sitting in nests). One site (#15) was identified 

as “territorial” only. At this site, an adult was sitting on the nest during nearly every nest 

check between 11 and 18 July, suggesting that egg-laying might have occurred during that 

period although the nest was clearly empty (i.e., no eggs or chicks) by 21 July (data not 

shown in Table 3). 

Table 3 - Summary of daily status for the nine Brandt’s Cormorants nests monitored from the 

mainland on Gualala Point Island, 1-18 July 2007.1,2 

Nest Status Day in July 2007 

# 1 2 3 4 5 6 7 8 9 10 11 12 16 17 18 

1 B N N N N N N N F T T T T T T T 

2 B N C N C N N C N C C C N N C ? 

3 B N N N N N N F T T T T T T T T 

4 B N N N N N N N N N N C N N C N 

13 B ? C N C C C N N C C C C ? C ? 

14 B N N N N N C N N C C C N C N ? 

15 T T T T T T T N? N? T? T? N N N N N 

16 B ? C N C C N N N C C C C N C ? 

18 B ? ? ? ? ? ? ? ? C C C ? N C ? 1

The numbered nests below are different from the schema used in Figure 2 and in Appendix 1. 2

Key to abbreviations: 

B = breeding site 

C = cormorant chick(s) seen 

F = failed nest 

N = adult sitting on nest 

N? = uncertain whether the site is a functioning nest 

T = territorial site (“status”) or adult at nest territory only (daily nest condition) 

T? = uncertain whether the site is functioning as a territory 

? = or no data (nest view obstructed or not checked) 

Chicks were not visible until they were large enough to be seen above the nest bowl, usually 

after seven to ten days of age. Of nests with chicks, the maximum numbers of chicks 

18 
recorded were: one chick at one nest; two chicks at four nests; and > 3 chicks at one nest. 

Four nests had chicks confirmed before the fireworks, and three more nests had chicks 

confirmed after the fireworks. Beginning on 9 July, some chicks were large enough to begin 

wandering from nests, when failed Nest #3 was sporadically visited by a wandering chick 

from another nearby nest. 

During the count period, two nests, or 22% of the sample, failed as indicated by a sudden 

change in adult behavior (e.g., standing outside the nest, irregular attendance), lack of eggs or 

chicks in nests when exposed to view, and deterioration of the nests. Nest #3 was found to 

be failed on 7 July and Nest #1 on 8 July (Table 3). Although these nests were fairly 

regularly (but not constantly) attended thereafter until at least 18 July, subsequent checks 

through 28 July showed no evidence of re-nesting. Because no chicks had been observed 

prior to nest failure, these nests likely were in the egg or early chick stage when they failed 

(Nest #3 had a possible egg observed on 1 July). 

Pelagic Cormorant: Two Pelagic Cormorant nests were located on the same ledge on the 

north side of Gualala Point Island (Figure 8). The number of nests was low in comparison to 

2006, when seven nests were recorded on the south side cliffs of the island (R. Kuehn, pers. 

comm.). 

Figure 8 – Images of the two Pelagic Cormorant nest sites on Gualala Point Island from three 

different dates, 1 to 12 July 2007. 

Pelagic Cormorants GPI-N 20070706 Pelagic Cormorants GPI-N 20070706 

Pelagic Cormorants GPI-N 20070707 Pelagic Cormorants GPI-N 20070711 

Photos © Rozanne Rapozo, Nature As I See It 

19 
In 2007, both nests monitored on Gualala Point Island failed. Pelagic Cormorant Nest #1 first 

showed signs of failure on 10 July when an apparently incubating adult departed the nest for 

several hours. Later the same day, the same or a different bird was observed sitting on the 

nest. Sporadic occupancy continued after 10 July but eggs or chicks were not observed and 

the nest was completely abandoned by 12 July. At Nest #2, adults incubating two or more 

eggs were observed through 12 July; by 16 July (outside the count period), this nest also was 

abandoned. 

Western Gull: Observers at both the north and south vantage points observed Western Gull 

nests and young in nests throughout the count period. Western Gull nests occupied either the 

relatively flat top surface at the east end of the island or wide ledges and nooks just below the 

top of the island. Thirteen nests on the north side and eight nests on the south side of the 

island were visible. Accounting for visual overlap between vantage points, a total of 

seventeen nests were observed daily for as long as the young gulls remained in or near the 

nest. Afterward it was not possible to distinguish nest origin of mobile chicks and loss of 

individual young could not be determined. 

All but four nests contained visible chicks by 2 July and all nests had chicks by 12 July. 

Brood sizes averaged 2.29 chicks (range = 2–3, n = 17); 29% of broods contained three 

chicks. No nest failures or chick fatalities were recorded during the count period. However, 

surveys of all chicks were often difficult to obtain because of high wind conditions, when 

chicks crouched out of the wind. As chicks grew larger, they were easier to detect, which 

may explain the continued rising trend in counts of mobile chicks toward the end of the count 

period, even though very few young hatched after 2 July. 

Harbor Seal Counts from Mainland Vantage Points 

Harbor Seals regularly hauled out along the intertidal perimeter of the island and less often 

above the mean high tide line. No Harbor Seal pups were recorded at Gualala Point Island 

during the count period. 

Seals were not double-counted during simultaneous counts from each vantage point. 

Therefore, counts from north and south vantage points were pooled for the total daily 

maximum count at the diurnal low tide (Figure 9). Because the counts took place as close to 

low tides as possible, Harbor Seal count times changed from day to day. 

In general, low-tide counts declined through the count period, with the lowest count on 7 

July. This observation suggests that there may have been a response that coincided with the 

fireworks display. However, at 21:00 h on 6 July, just before the Gualala fireworks display 

began and the island was still visible, Task Force observers did not locate any Harbor Seals 

from either vantage point on Gualala Point Island. Thus, a link between a decline in numbers 

on 7 July and the fireworks display is not conclusive. 

20 
Figure 9 – Census of Harbor Seals at daytime low tide, Gualala Point Island, 1 to 12 July 

2007. 

0

5

10

15

20

1 2 3 4 5 6 7 8 9 10 11 12

Day in July 2007 

N

u

m

ber of S

eals 

Daytime Disturbance Monitoring 

Aircraft and boat disturbances have been shown to impact certain seabird colonies in central 

California and elsewhere (Carney and Sydeman 1999, Rojek et al. 2007). To assess overall 

agents of disturbance and their effects at Gualala Point Island, all potential human 

disturbances and all non-human disturbances were recorded during daytime seabird counts 

(Table 4). Daytime disturbance agents and disturbances to seabirds, whether human- or 

animal-caused, were rare and minor during the count period. Two disturbances were from 

cannon blasts and one from a fishing boat. Of all aircraft recorded, only the jets and 

helicopter flew below 300 m but still did not cause any notable disturbance. The fishing boat 

that caused two Brandt’s Cormorants to flush had approached to within 45 m of the island. 

Table 4 – Summary of daytime disturbances to seabirds on Gualala Point Island recorded 

during seabird counts and nest surveys, 1-12 July 2007. 

Disturbance Agent 

Total 

Number 

of Events 

Total Duration 

in Minutes 

Number of 

Disturbance 

Events 

Effect on Seabirds 

Aircraft 

Airplane 7 14 0 none 

Military Jets (4) 1 1 0 none 

Helicopter 1 1 0 none 

People on Beach 1 22 0 none 

Cannon Blast 3 3 2 Brandt’s Cormorants assumed an 

alert posture, did not flush 

Fishing Boats 6 25 1 2 Brandt’s Cormorants flushed 

Avian Sources

 Brown Pelican 1 1 1 20 Western Gulls flew up, called 

 Western Gull 1 1 1 other gulls became agitated 

Unknown 1 2 1 20 to 30 Western Gulls flushed 

Total 22 70 6 -- 

21 
Data Collection during the Gualala Festivals Committee Fireworks Display, 

6 July 2007 

The South Coast Fire Protection District issued a permit, dated 13 June 2007, to the Gualala 

Festivals Committee to detonate 732 three-inch shells containing fireworks during an interval 

of ten minutes. The fireworks display ran from 21:35 to 21:53 h on 6 July 2007. A bird 

count, taken at 21:00 h while light conditions still permitted complete coverage, included 

nineteen Brandt’s Cormorants, eight Pigeon Guillemots, one Black Oystercatcher and about 

100 Western Gulls on the island. 

Observers did not tally the number of detonations during that time. However, the detonations 

were continuous for the entire eighteen-minute interval. In contrast with the permit issued 

for the 2006 display, the 2007 permit covered a narrower spectrum and less powerful 

selection of fireworks to display. 

Weather conditions during the fireworks display were clear with a strong northwest wind 

onshore, but a fog bank was present offshore. 

During the fireworks display, two observers viewed and verbalized observations to a third 

observer who recorded observations. The following are verbatim observations recorded at 

the south vantage point viewing Gualala Point Island: 

“At 9:35 pm the fireworks began with no loud ‘salutes’ but with light burst[s] and pops. 

There was lots of noise from the birds as soon as the fireworks started. We heard the bird 

cries from 1000 feet away. The gulls are up and flying immediately and constantly calling. 

Cormorants are moving around at the nest area; a few are up and flying also. Birds are 

flying higher and higher. Lots of bird noise. Birds are high enough to silhouette above the 

fog bank. None are seen landing at this time. Birds are up 11⁄2 times higher than the 

island’s height. Fireworks ‘pop’ every 1 to 11⁄2 seconds. No break between fireworks; 

steadily shot off. About 9:45 pm it is quieter: we cannot hear the gulls nor see them in 

flight. Have they landed? About 9:50 pm we lost visibility to the dark and the fog bank 

background. The right corner of the upper face of Gualala Point Island is lit up 3 times by 

fireworks. The finale is very loud and frequent explosions. Right face of the rock is lit up. 

Birds are flying again and calling loudly through the finale. 18 minutes total disturbance 

time.” 

During these observations, “bird noise” referred to Western Gulls, a vocal species. Most 

other seabird calls, such as from cormorants, were not audible from the mainland vantage 

points. The cormorants observed referred to Brandt’s Cormorants. In the darkness, 

observers were not able to obtain data on Pelagic Cormorants, Black Oystercatchers, or 

Pigeon Guillemots. 

Nighttime Photography and Audio Recording: Photographers took pictures set for nighttime 

exposures on two evenings during the count period. On 4 July 2007, photographs taken at 

thirty-second exposures monitored Western Gull and Brandt’s Cormorant behavior for 80 

minutes after sunset. Minimal bird activity was noted during this time; both cormorants and 

gulls appeared to be in the same positions from image to image. 

22 
On 6 July 2007, photographic images of the Brandt’s Cormorant colony were taken from 55 

minutes prior to the start of the fireworks display until 22:00 h. Prior to the fireworks, 

activity of Brandt’s Cormorants and Western Gulls was minimal; birds were in the same 

relative positions from image to image. In the images acquired at 21:35 h just after the start 

of the fireworks, cormorants had changed postures from resting to standing and alert. By 

21:36 h, some birds had moved from their original locations to points on the tops of rocks. 

By 21:37 h at least six birds were gone from their positions, having either flushed or 

otherwise moved out of view. In the next four minutes, at least three other birds departed 

and one other bird moved to a position higher on the rock. In one example, a resting 

cormorant first became alert, looked to the left, then looked to the right, and then lifted off 

and departed the colony. 

Audio was recorded with a hand-held video camera during the fireworks. An iMovieTM slide 

file with the synchronized Western Gull calls was made. High winds appeared to dampen the 

sounds of the gulls and fireworks at the observation site. Additional photographs and sound 

recordings are on file with The Sea Ranch Association. 

Acoustical Readings: No data on acoustical readings are reported here. A windscreen used 

did not adequately shield the sound recording instrument, and the wind turbulence caused 

high background readings. Further sound analysis will require more complex filtering of 

background noise from this procedure. Task Force members and BLM biologists will work 

further to analyze the recordings with software for generating sound spectrograms. 

Data from the fireworks operator were not available for comparing sound levels of the 

fireworks displays in 2006 and 2007. 

Discussion 

Short-term Impacts 

This study was the first to examine colony attendance patterns and relative breeding parameters 

for seabirds and marine mammals at Gualala Point Island. The impetus for the study was to 

examine potential impacts of a fireworks display conducted from a low coastal bluff 1.8 km from 

the island on 6 July 2007. Data also provide baseline information that will be valuable for 

guiding future monitoring efforts, management, or other studies. Surveys demonstrated the same 

five species of seabirds nesting on Gualala Point Island in 2007 as in the previous complete 

survey of the island in 1989 (Carter et al. 1992). Breeding populations of most species also were 

similar to 1989 except for Brandt’s Cormorant, which has declined substantially. 

While data were collected on all species observed, efforts focused on the colony of Brandt’s 

Cormorants because of their known sensitivity to human disturbance (Hunt et al. 1981, 

McChesney 1997, Wallace and Wallace 1998, Thayer et al. 1999) and the relatively large sample 

size that could be monitored. For this species, colony monitoring combined land-based nest 

monitoring and bird counts with data from a series of aerial photographs. The aerial 

photography established “snapshots” in time and provided coverage of the entire cormorant 

colony. Land-based nest monitoring, however, was limited because only about 10% of the 

colony was visible from the mainland vantage point. Still, land-based nest monitoring provided 

23 
relatively detailed information on the nests that could be viewed and helped interpret aerial 

photographic results. 

From the aerial photographs, 90 breeding pairs of Brandt’s Cormorants were identified on 

Gualala Point Island in 2007. Overall, 78% of nests were successful through 12 July (but may 

have been lower if additional nests failed after 12 July). Most (70%) nests that failed did so 

within a short, seven-day interval between 5 and 12 July, and 35% of nest failures occurred over 

just two days between 5 and 7 July. Nest success was lower than Brandt’s Cormorant nest 

success in 2007 at three central California colonies: 86%, 90%, and 97% at Castle Rocks and 

Mainland (Monterey County), Devil’s Slide Rock and Mainland (San Mateo County), and Point 

Reyes (Marin County), respectively (G. J. McChesney, USFWS, unpubl. data). At these 

colonies, nest failures occurred infrequently and asynchronously over the course of the season, 

and most nest failure occurred prior to 6 July. 

Nighttime monitoring during the 6 July fireworks display demonstrated visible disturbance to 

both Brandt’s Cormorants and Western Gulls on Gualala Point Island. The cormorants became 

visibly alert immediately after the start of the display, followed shortly by birds being displaced 

and flushed. Western Gulls also flushed and flew over the island. These responses coincided 

with high rates of Brandt’s Cormorant nest abandonment in the days immediately after and 

shortly following 6 July. During severe disturbance events, cormorants may depart their nests, 

leaving eggs and chicks susceptible to predators such as gulls or they may accidentally kick eggs 

out of the nest (McChesney 1997, Wallace and Wallace 1998). Following the cessation of the 

disturbance, birds may either return to their nests or they may abandon nesting efforts entirely. 

Thus, it is highly likely that nests found to be failed on 7 July were associated with the fireworks 

disturbance the previous evening. 

For Brandt’s Cormorant nests found to be failed after 7 July, the causes for failure are less clear 

but also may have been associated with the fireworks disturbance. Brandt’s Cormorants 

sometimes will attend nests for up to several days after nest failure, even refurbishing and sitting 

in the nest (G. McChesney, pers. obs.). Thus, it is possible that some nests recorded as “active” 

on 7 July actually had already failed but that adults were still attending nests, which visibly 

failed a few days later. Other factors associated with the fireworks display also may have 

contributed to a prolonged period of nest failure. For example, at certain colonies with high 

levels of human activity, high nest loss over longer periods has been demonstrated in other 

seabirds even in the absence of obvious behavioral cues (Giese 1996, Beale and Monaghan 

2004). High stress caused by human disturbance was thought to be the cause. Based on 

behavioral observations in this study, cormorants and other birds almost certainly experienced 

elevated stress levels during the fireworks display and this may have had an effect lasting up to 

several days. Also, if a cormorant mate had been disturbed by the display and subsequently 

abandoned the island, the breeding pair’s nest certainly would have failed because two parents 

are necessary for cormorants to nest and rear young successfully. 

The fact that most cormorant nests abandoned were on the edge of the colony was not surprising. 

Studies of other seabirds have shown that birds nesting on the edge or in low-density portions of 

a colony can experience higher rates of nest predation and lower breeding success than nests in 

the interior or denser parts of colonies (Birkhead 1977, Siegel-Causey and Hunt 1981). Also, 

nests established later and still holding eggs or small chicks were more prone to predation by 

gulls (e.g., Birkhead 1977). Larger chicks, such as chicks in many nests on 6 July, are generally 

24 
too large for avian predators to handle and are capable of maintaining their body temperatures to 

survive brief periods of exposure when adults are absent (Ainley and Boekelheide 1990). None 

of the cormorant nests known to have failed on Gualala Point Island between 7 and 12 July had 

large chicks. 

Data were not adequate to fully evaluate potential impacts of the fireworks display on other 

species. However, for the entire day on 7 July, Western Gulls showed a brief but marked decline 

in numbers of adults counted on Gualala Point Island. This decline may have been associated 

with disturbance to gulls recorded the previous night during the fireworks display. 

Potential Long-term Impacts 

The Brandt’s Cormorant is one of the most abundant breeding seabirds in California (Sowls et al. 

1980, Carter et al. 1992). However, along the southern Mendocino County and Sonoma County 

coasts, few colonies exist mainly because suitable breeding habitat is scarce. Formerly, Gualala 

Point Island was the largest of only a handful of Brandt’s Cormorant colonies between Point 

Arena and Bodega Bay. Available data indicate that the Brandt’s Cormorant colony at Gualala 

Point Island has declined substantially since 1980. The count of 65 nests on 30 May 2007 was 

the lowest recorded to date during standardized USFWS annual surveys (Sowls et al. 1980; 

Carter et al. 1992 and 2000; Capitolo et al. 2004; and this study). 

Fireworks displays are not the major cause for the long-term decline of Brandt’s Cormorants on 

Gualala Point Island. A specific cause or set of causes remains unknown at this time. Given the 

sensitivity of Brandt’s Cormorants to disturbance and the proximity of the colony to various 

human-related activities, human disturbance may be at least partially responsible for reductions 

in numbers. Thus, a major concern is that additional human disturbances, such as the recently 

instituted fireworks display, will add to the burden of impacts and will make future recovery of 

the colony less likely. 

Common Murres, a species recovering in California from past human impacts that is undergoing 

a breeding population expansion in southern Mendocino County (Carter et al. 2001, Capitolo et 

al. 2006), were observed prospecting on several days in 2007 among the Brandt’s Cormorant 

colony on Gualala Point Island. If properly protected, murres may begin nesting on the island in 

the near future and become the first documented colony in Sonoma County. 

In addition to the importance of Gualala Point Island to nesting and roosting seabirds, the coast 

between Collins Landing and the Gualala River has been important for certain species, especially 

Pelagic Cormorants (Sowls et al. 1980, Carter et al. 1992). This species, which nests in more 

scattered and lower-density colonies, is also sensitive to both disturbance and shortages in prey 

supplies (Carter et al. 1984, Ainley and Boekelheide 1990). Given the similar proximity to 

developed areas, this local colony also may be jeopardized by increases in human disturbance. A 

remnant population of the federally threatened Marbled Murrelet (Brachyramphus marmoratus) 

uses the waters just off the mouth of the Gualala River (C. S. Strong, Crescent Coastal Research, 

pers. comm.). Intensifying human disturbance could jeopardize the well-being of this small 

group of birds. 

25 
LITERATURE CITED 

Ainley DG; Boekelheide, RJ, eds. 1990. Seabirds of the Farallon Islands: ecology, 

dynamics and structure of an upwelling-system community. Stanford, CA: Stanford 

University Press. 450 pp 

Beale, CM; Monaghan, P. 2004. Human disturbance: people as predation-free predators? 

Journal of Applied Ecology 41:335-343. 

Birkhead, TR. 1977. The effect of habitat and density on breeding success in the Common 

Guillemot (Uria aalge). Journal of Animal Ecology 46(3): 751-764. 

Capitolo, PJ; Carter, HR; Young, RJ; McChesney, GJ; McIver, WR; Golightly, RT; Gress, F. 

2004. Changes in breeding population size of Brandt’s and Double-crested cormorants in 

California, 1975-2003. Unpublished final report for contract #10154-2-G106 between 

Humboldt State University Foundation and USDI Fish and Wildlife Service. Arcata, CA: 

Humboldt State University, Department of Wildlife. 51 pp 

Carney, KM; Sydeman, WJ. 1999. A review of human disturbance effects on nesting colonial 

waterbirds. Waterbirds 22(1): 68-79. 

Carter, HR; Capitolo, PJ; McChesney, GJ; McIver, WR; Takekawa, JE. 2000. Population 

monitoring of seabirds in California: colony and subcolony databases for 1985-1995 surveys 

of breeding colonies of Common Murres, Brandt’s Cormorants, and Double-crested 

Cormorants between Point Arena and Point Conception. Unpublished report. Dixon, CA: US 

Geological Survey, Western Ecological Research Center. 71 pp 

Carter, HR; Hobson, KA. 1988. Crèching behavior of Brandt’s Cormorant chicks. Condor 

90(2): 395-400. 

Carter, HR; Hobson, KA; Sealy, SA. 1984. Colony-site selection by Pelagic Cormorants 

(Phalacrocorax pelagicus) in Barkley Sound, British Columbia. Colonial Waterbirds 

7(1):25-34. 

Carter, HR; McChesney, GJ; Jaques, DL; Strong, CS, Parker, MW; Takekawa, JT; Jory, DL; 

Whitworth, DL. 1992. Breeding populations of seabirds in California, 1989-1991. 

Unpublished draft report, 2 volumes. Dixon, CA: USDI Fish and Wildlife Service, Northern 

Prairie Wildlife Research Center. Various pagination 

Carter, HR; Wilson, UW; Lowe, RW; Rodway, MS; Manuwal, DA; Takekawa, JT; Yee; JL.. 

2001. Population trends of the Common Murre (Uria aalge californica). In: Manuwal, DA; 

Carter, HR; Zimmerman, TS; Orthmeyer, DL, eds. Biology and conservation of the 

Common Murre in California, Oregon, Washington, and British Columbia. Volume 1: 

Natural History and population trends. Information and Technology Report, 

USGS/BRD/ITR-2000-0012. Washington, DC: USDI US Geological Survey. pp 33-132. 

Ewins, PJ. 1993. Pigeon Guillemot (Cepphus columba). In: Poole, A; Gill, F, eds. The Birds 

of North America. No. 49. Philadelphia, PA: The Academy of Natural Sciences. 

26 
Giese, M. 1996. Effects of human activity on Adelie Penguin Pygoscelis adeliae breeding 

success. Biological Conservation 75:157-164. 

Hunt, GL, Jr.; Pitman, RL; Naughton, M; Winnett, K; Newman, A; Kelly, PR; Briggs, KT. 

1981. Summary of marine mammal and seabird surveys of the Southern California Bight 

area 1975-1978. Vol. III – Investigators’ Reports. Part III. Seabirds – Book II. Publication 

PB-81-248-05. Springfield, VA: US Department of Commerce, National Technical 

Information Service. 337 pp 

Jaques, D; Strong, C. 2002. Disturbance to Brown Pelicans at communal roosts in southern 

and central California. Report prepared for the American Trader Trustee Council. Astoria, 

OR: Crescent Coastal Research. 26 pp 

Manna, J; Roberts, D; Press, D; Allen, S. 2006. Harbor Seal monitoring: San Francisco Bay 

area. Point Reyes Station, CA: USDI Point Reyes National Seashore. 22 pp 

McChesney, GJ. 1997. Breeding biology of the Brandt’s Cormorant on San Nicolas Island, 

California. M.S. Thesis. Sacramento, CA: California State University. 201 pp 

McChesney, GJ; Eigner, LE; Poitras, TB; et al. 2007. Restoration of Common Murre 

colonies in central California: annual report 2006. Unpublished report, US Fish and Wildlife 

Service, San Francisco Bay National Wildlife Refuge Complex, Newark, California. 70 pp 

Rojek, NA; Parker, MW; Carter, HR; McChesney, GJ. 2007. Aircraft and vessel disturbances 

to Common Murres Uria aalge at breeding colonies in central California, 1997–1999. Marine 

Ornithology 35(1): 67–75. 

Siegel-Causey, D; Hunt, GL, Jr. 1981. Colonial defense behavior in Double-crested and 

Pelagic cormorants. Auk 98(3): 522-531. 

Sowls, AL; DeGange, AR; Nelson, JW; Lester, GS. 1980. Catalog of California seabird 

colonies. Report FWS/OBS 37/80. Washington, DC: USDI Bureau of Land Management / 

Fish and Wildlife Service, Office of Biological Services, Coastal Ecosystems Project. 371 pp 

Thayer, JA; Sydeman, WJ; Fairman, NP; Allen, SG. 1999. Attendance and effects of 

disturbance on coastal Common Murre colonies at Point Reyes, California. Waterbirds 22(1): 

130-139. 

USDI Bureau of Land Management; The Sea Ranch CCNM Stewardship Task Force. 2008. 

Protocol documentation for seabird and marine mammal monitoring on offshore rock islands 

in Sonoma and Mendocino counties, California: 2007. Unpublished report. Sacramento, CA: 

USDI Bureau of Land Management, California State Office. 46 pp. 

Wallace, EAH; Wallace, GE. 1998. Brandt’s Cormorant (Phalacrocorax penicillatus). In 

The Birds of North America, No. 362 (A. Poole and F. Gill, eds.). The Birds of North 

America, Inc., Philadelphia, PA. 

27 
Wengert, Greta M.; Gabriel, Mourad W. 2002. Waterbird chick mortality associated with 

fireworks during the breeding season. Manuscript. McKinleyville, CA: Integral Ecology 

Reseach Center. 11 pp 

28 
Appendix 1 

Histories of Brandt’s Cormorant nest and territorial sites recorded in aerial 

photographs, Gualala Point Island, 30 May to 12 July 2007.1 

Nest # Status 30 May 5 June 5 July 7 July 12 July 

Fate as of 

12 July 

1 B V V SF SF SW S 

2 B V T SF SF failedT F 

3 B V SF SW SW SW S 

4 B V SF SW SW failedDE F 

5 B SW SW SW SW SW S 

6 B V V SW failedDE T F 

7 B DPE SF failedV V V F 

8 B SF SW SW SW SW S 

9 B SF SF SW SW SW S 

10 B T SF SW SW failedDE F 

11 B V SF SF SW SW S 

12 B SF SW SW SW SW S 

13 B SW SW SW SW SW S 

14 B SW SW SW SW DC S 

15 B SW SW SW SW DC S 

16 B SW SF SW failedE T F 

17 B SW SW SW SW SW S 

18 B SW SF SW SW SWG S 

19 B SW SW DC DC DC S 

20 B V SW SW SW SW S 

21 B SW SF SW SW DC S 

22 B SW SW DW DC DC S 

23 B SW SW SW SW DC S 

24 B SW SW SW SW C S 

25 B SW SW DC DC DC S 

26 B SW SW DC DC DC S 

27 B SF SW SF SF SW S 

28 B SW SW DC DC DC S 

29 B SW SW failedT V 

DF(E in 

alt photo) F 

30 B SW SW SW SW SW S 

31 B SW SW DC SW DC S 

32 B SW SW SW SW SW S 

33 B V SP SF SF DC S 

34 B SW SW DC SW DC S 

35 B T SF SF SW SW S 

36 B SW SW SW failedE 

SW(E in 

alt photo) F 

37 B SW SW SW SW DC S 

38 B SW SW SW DC DC S 

39 B SF SW SW SW DC S 

40 B T SP SF failedV DC F 

41 B SF SW SW SW DC S 

42 B T SP SW SW SW S 

29 
Nest # Status 30 May 5 June 5 July 7 July 12 July 

Fate as of 

12 July 

43 B SW SW failedV V V F 

44 B SW SW SW DC DC S 

45 B SW SW DC DC DC S 

46 B SW SF SF SW SW S 

47 B SW SW SW SW DC S 

48 B SW SW SW SW SW S 

49 B SW SW SW SW DC S 

50 B SW SW DW SW DC S 

51 B V SF SF failedV T F 

52 B SP SW failedDPE V V F 

53 B SW SW SW SW DC S 

54 B T SF SW SF SW S 

55 B SF SF SW failedE DC F 

56 B SW SW DC DC DC S 

57 B SW SW SW DC DC+ S 

58 B SW SF DW SC DC S 

59 B SW SW DC SW DC S 

60 B SW SW failedDE V T F 

61 B SF SF DW DC DC S 

62 B SW SW SW SW failedDE F 

63 B SW SW DC SW DC S 

64 B SW SW DC DC DC S 

65 B DPE SF SW SW DC S 

66 T T SP T V DC na 

67 B T SF SW SW SW S 

68 B T SW SW SW SW S 

69 B V SW SW SW SW S 

70 B SW SW SW SW failedV F 

71 B V SW SW SW DC S 

72 B SW SW SW SW DC S 

73 B SW SW SW SW DC S 

74 B SW SF SW SW SF S 

75 B V SF SF SF SF S 

76 T T DF V V V na 

77 B SW SW SW SW failedDE F 

78 B SW SF SW failedE DC F 

79 B SW SW SW SW DC S 

80 B SP SF SW SW DC S 

81 B SW SF SW SW SW S 

82 B SW SW SW SW DC S 

83 B SW SW SW SW DC S 

84 B SW SW SW SW DC S 

85 B SF SF SF SW DC S 

86 B SP SF failedV V V F 

87 T V T V V V na 

88 B SW SW DC DC DC S 

89 B SW SW SW SW DC S 

90 B SW SF SW SW DC S 

30 
Nest # Status 30 May 5 June 5 July 7 July 12 July 

Fate as of 

12 July 

91 B SF n/a SF SF SFG S 

92 B DF n/a SW SW failedV F 

93 B SF SF SW SW SW S 1

 Codes are as follows: 

Status: B = breeding site 

T = territorial site 

Nest Site Condition by Date: C = chick(s) visible in nest 

D = adult standing at nest site 

E = empty nest 

F = fairly well built nest 

G= egg(s) visible in nest 

P = poorly built nest 

S = adult sitting on nest 

T = adult bird(s) on territory with little or no nest material 

V = vacant site 

W = well built nest 

failed = first survey when nest discovered to be failed 

n/a = no photo coverage 

Fate as of 12 July: F = failed 

S = successful 

 n/a = no nest established during the count period 

31 
Appendix 2 

Bird Census Totals by Species, Vantage Point and Time of Day, 1 to 12 July 2007 

0 = no birds observed – = no data available because of poor visibility 

32 
33 
34 
35 
36 
37 
38