Collins, C.T. and K.L. Garrett. 1996. The Black
Skimmer in California: An overview. Western Birds 27:127-135.
NOTES: Reviews "the status of the Black Skimmer in California with emphasis on the size and location of breeding colonies and overwintering aggregations." This species has undergone an increase in range and abundance over the last few decades.
Dritschilo, W., and D. Vander Pluym. 1984. An exotoxicological model for energy development and the Salton Sea, California. Journal of Environmental Management 19:15-30.
Grant, G.S. and N. Hogg. 1976. Behavior of
late-nesting Black Skimmers at Salton Sea, California. Western
Birds 7: 73-80.
ABSTRACT: The Black Skimmer (Rynchops niger) was first found nesting at the south end of the Salton Sea, Imperial County, California in 1972 (McCaskie et. al. 1974). Five nests were found in 1972, three in 1973, (McCaskie, 1973), and three in 1974 (McCaskie, 1974). Nesting had been suspected at the north end of the Sea, but was not confirmed until 16 August 1975 when the authors, Sandra Grant and Jeanne Hogg discovered eight nests on a small barnacle-covered island in the northeast corner of the sea. Biweekly visits were made to the island and several aspects of their breeding behavior are reported here.
Grinnell, J. 1908. Birds of a voyage on Salton
Sea. Condor 10:185-191.
NOTES: Account of a two-day boating excursion on the Salton Sea in April 1908 [when its elevation was approx. &endash;200 ft and its salinity approx. 17 g/L]. Notes high abundance of carp, bonytail, and catfish, and of fish-eating birds: Double-crested ("Farallone") Cormorants, Western Grebes, Common Loons, White Pelicans, Great Blue Herons, Caspian Terns. Also observed were Ring-billed Gulls and 15 groups of 20-50 Eared Grebes each. White Pelican colony of 980 occupied nests was observed on Echo Island, about 12 miles "south of Lano"; this was southernmost known nesting location for the species. Three miles away on Pelican Island there was a Double-crested Cormorant colony with 147 nests with eggs plus 7 Great Blue Heron nests with eggs and 3 pelican nests with eggs. Two and three years earlier this was the main pelican nesting ground in the lake.
Grinnell, J. 1914. An account of the mammals and birds of the lower Colorado Valley. Univ. Calif. Pub. Zool. 12: 51-294.
Jehl, J.R., Jr. 1988. Biology of the Eared
Grebe and Wilson's Phalarope in the nonbreeding season: A study of
adaptations to saline lakes. Studies in Avian Biology
ABSTRACT : The Eared Grebe (Podiceps nigricollis) and Wilson's Phalarope (Phalaropus tricolor) are among the most halophilic species of birds in the world. Immediately after the breeding season, thousands congregate at saline lakes in the western United States and Canada to prepare for their eventual migration to wintering grounds. For grebes, these are mainly the Salton sea and Gulf of California; for phalaropes they are salt lakes in the central Andes.
From 1980 to 1987 I studied the postbreeding biology of both species at Mono Lake, California. This permanent saline and alkaline lake on the western edge of the Great Basis is one of the largest molting and staging areas in the world for each species. Abundant invertebrate prey in the form of brine flies (Ephydra hians) and brine shrimp (Artemia monica) provide the major attraction for these and a few other migratory bird species.
Eared Grebes may be found at Mono Lake at any season. The summering flock of nonbreeders often numbers 25,000 or more. Tens of thousands of postbreeding birds begin arriving in late July. Adults use the lake as the terminus for a molt migration. they continue to be joined through early fall by adults that have molted elsewhere as well as by juveniles, so that by early October nearly 750,000 grebes may be present. This is 30% of the North American fall population of 2,500,000. They stage there until food supplies fail and then migrate to wintering areas. The Mono Lake flock seems to be derived from the western sector of the breeding range.
The grebes feed primarily on brine flies through early summer, then shift to brine shrimp for the remainder of the year. In fall, shrimp comprise >98% of the diet, and at peak numbers grebes probably consume 60 to 100 tons of shrimp daily.
Shortly after arriving, adults molt their remiges simultaneously. This process does not begin until after the birds have begun to gain weight, which event presumably signals that environmental conditions are acceptable for risking 34-40 days of flightlessness. After completing wing molt, the birds remain continuously at Mono Lake and do not fly for months. During molt, their breast muscles atrophy. Nevertheless, they continue body molt and concurrently lay on vast fat stores, more often than doubling their arrival weights. To regain flying condition and to be able to resume migration, they metabolize fat reserves during a period of forced fasting but simultaneously rebuild breast muscles, in part by exercise. This takes approximately two weeks. Fat deposits are laid down when food is superabundant probably ensure that the birds have sufficient energy to complete the molt and migrate should prey populations fail, but may have additional functions as well.
While at Mono Lake the grebes undergo pronounced daily and seasonal shifts in distribution, which in periods of food scarcity are controlled by the distribution of prey. Tufa shoals are a favorite feeding locality. Differences in distribution of age groups are evident, juveniles often being relatively more abundant nearer shore. Daily movements do not involve visits to fresh water; the birds satisfy their water requirements from the body fluids of their prey.
Beached-bird censuses revealed that mortality was highest in early spring and around the main southward departure period in late fall. Even so, over the entire year, mortality at Mono Lake was trivial, probably involving no more than 0.5% of the fall population. Juveniles suffered higher losses than older birds, perhaps because of their later average arrival time and presumed inefficiency in foraging. Food shortages and downings due to bad weather during migration are likely the major causes of mortality. The risk of large die-offs in migration seems highest in years when invertebrate populations remain large into late fall, enticing the grebes to linger into periods of severe winter storms.
Small numbers of Wilson's Phalaropes pass through the Mono Basis in spring. Fall migrants occur between mid-June and late September. the earliest arrivals are adult females, which comprise 70% of the population; these are followed by adult males (30%) in early July, and finally by juveniles (<2%) in mid-July and early August. Peak numbers are reached in late July, when the southward exodus begins. Most adult females depart by 5 August, adult males by 15 August, and juveniles by 5 September.
Jehl, J. R. Jr. 1993. Observations on the fall migration of eared grebes, based on evidence from a mass downing in Utah. The Condor 95:470-473.
ABSTRACT: After the breeding season in North America, most Eared Grebes (Podiceps nigricollis) migrate to highly saline lakes in the Great Basin to molt and stage for several months. During this period they molt, undergo a cycle of breast muscle atrophy and hypertrophy, and accumulate huge fat deposits before flying to wintering areas (Jehl 1988, unpubl. manucsript; Gaunt et al. 1990).
On 10 December 1991 thousands of grebes departed Great Salt Lake en route to the Salton Sea, California, or Gulf of California, Mexico. Their route was south-westerly, and for the first 500 km--roughly between Salt Lake City and the Arizona border--paralleled Interstate Highway 15 and the Wasatch Mounrains, which are slightly to the east. Several hours into the flight, over southern and central Utah, large numbers were forced down by a snowstorm along a 180 km stretch between Holden and Cedar City; a few were also reported in the Provo/Springfield area (Fig. 1). The birds did not fall uniformly, but apparently were attracted to lights from towns and highway intersections. Many died when they crashed to earth; others were hit by cars on the highway, which they evidently mistook for open water. Thousands more were captured alive and released on whatever local water bodies remained open.
Most of our current understanding about the biology of Eared Grebes in fall migration is based on studies of birds staging at Mono Lake, California (Jehl 1988). The data from this downing provided an opportunity to test and extend some earlier findings or inferences about the differential migration of age classes, duration of the flight to wintering areas, physical condition of departing and arriving migrants, the size of pectoral muscles needed for flight, and the risks of mortality along the migratory routes (Jehl 1988, Gaunt et al. 1990).
Jehl, Joseph R. Jr. 1994. Changes in saline and
alkaline lake avifaunas in western North America in the past 150
years. Studies in Avian Biology No. 15:258-272.
ABSTRACT: I use biological, historical and limnological data to consider how changes at some of the major saline and alkaline lakes in the western United States may have affected their ability to support breeding and migratory birds in the past 150 years. I emphasize hypersaline lakes (salinities >50%), where the birdlife is dominated by a few species, principally California Gull, Wilson's Phalarope, Rednecked Phalarope, and Eared Grebe, that can exploit the abundant invertebrate prey resources. Of eight lakes treated in detail, two have been irretrievably lost, and the long-term survival of another is questionable. Major engineering modifications are planned or in effect at three others. Only two or three lakes seem likely to be able to support their current avifaunas well into the next century.
Jehl, J.R., Jr., S.I. Bond, P. Unitt, and G.
McCaskie. 1977. Annotated bibliography on seasonal movements of
migratory and resident birds in the California desert. H/SWRI
Technical Report No. 77-105. Prepared for U.S. Bureau of land
Management, Riverside, CA.
ABSTRACT: Each year great numbers of migrating birds pass across the deserts of the southwestern United States while migrating between their wintering and breeding localities. The extent of trans-desert movements and the species involved in them are known only generally. The major goals of this study were to analyze the existing literature as well as unpublished data to provide a more thorough understanding, and to design field investigations that would provide further information of the migrations and on the use of the desert by migrants. This paper is based on a full analysis of the literature through 1976. The data suggest that most birds cross the desert over a broad front. They may use oases during the day, but there is no evidence that they pass across inhospitable terrain by moving from oasis to oasis.
Records of migratory species in the desert often refer to immature birds, suggesting that it is the young and inexperienced birds that are forced to land there. By inference, adults often pass across the area in a single flight. General patterns are summarized for each taxonomic group. The report also contains a fully annotated bibliography on the ornithology of the California Deserts; recommendations for additional field studies; and detailed appendices, including seasonal check lists for each of the subareas recognized.
Jehl, J. R, Jr., and S. I. Bond. 1983.
Mortalitiy of Eared Grebes in Winter of 1982-83. American
ABSTRACT: A minimum of 25,000 Eared Grebes (Podiceps nigricollis) died along the Pacific coast of southern California and Baja California in mid to late January 1983. Although the cause of the mortality cannot be established with certainty, we argue that the grebes were foeced down by bad weather during a trans-Sierra crossing after leaving Mono Lake, California. Those that survived reached the coast in such poor condition that they soon succumbed. If this explanation is correct, the die-off is likely to have been nuch greater than we can document, because grebes require open water from which to become airborne, and birds forced down in the mountains or deserts would likely have been unable to resume their journey.
McCaskie, G. 1970. Shorebird and waterbird use
of the Salton Sea. California Fish and Game 56: 87-95.
ABSTRACT: The Salton Sea, California, has a rich avifauna. Thirty-five species of shorebirds and 47 species of waterbirds, exclusive of swans, ducks, geese, cranes, and rails, have been recorded. Birds are particularly abundant during migration periods. A complete listing of birds is given, together with comments on abundance and seasonal occurrence.
McCaskie, G. 1973. The nesting season. Southern Pacific Coast region. American Birds 27:917-920.
McCaskie, G. 1974. The nesting season. Southern Pacific Coast region. American Birds 28:948-951.
McCaskie, G., S. Liston and W.A. Rapley. 1974. First nesting of Black Skimmers in California. Condor 76:337-338.
McCaskie, G. and S. Suffel. 1971. Black Skimmers at the Salton Sea, California. California Birds 2:69-71.
Miller, L. and A.J. Van Rossem. 1929. Nesting
of the Laughing Gull in southern California. Condor
NOTES: Mentions discovery of Gull-billed Tern colony on island in the Salton Sea in 1927. Recounts finding on sand islands in June 1928 two Laughing Gull nests with eggs and collecting three adults. Claims this is first record of the presence of this species "from the Pacific coast north of the tropics."
Molina, K.C. 1996. Population status and
breeding biology of Black Skimmers at the Salton Sea, California.
Western Birds 27:143-158.
SUMMARY: Black Skimmers nesting at the Salton Sea now form one of the largest nesting populations in western North America, numbering nearly 500 pairs in 1995. This unique inland population varies widely inpopulation size, havitat availability, and reproductive success. Nesting in one of the harshest environments in North America, it may be subject to enormous physiological stress. The increasing salinity and pollutant levels of the Salton Sea also contribute to the uncertain future of these and other piscivorous birds residing there. These baseline demographic data and a maturing banded population provide the foundation upon which more detailed studies of the ecology and physiology of this interesting population of Black Skimmers can be based.
Ohlendorf, H.M., and K.C. Marois. 1990.
Organochlorines and selenium in California night-heron and egret
eggs. Environmental Monitoring and Assessment 15:91-104.
ABSTRACT: Exceptionally high concentrations of DDE were found in blck-crowned night-heron (Nycticoraz nycticorax) (geometric mean 8.62µg/g wet wt.) and great egret (Casmerodius albus) (24.0 µg/g) collected from the Imperial Valley (Salton Sea), California in 1985. DDE concentrations in 14 of the 87 (16%) randomly selected night-heron eggs from six colonies (two in San Francisco bay, three in the San Joaquin Valley, and one at Salton Sea) were higher than those associated with reduced reproductive succsss of night-herons (8 µg/g). In addition, mean shell thickness of night-heron eggs collected from the San Joaquin Valley and from San Francisco Bay during 1982-1984 was significantly less than pre-DDT thickness and was negatively correlated (r = -0.50, n = 75, P<0.0001) with DDE concentration. Mean selenium concentration in night-heron eggs from Salton Sea (1.10 µg/g) was significantly higher than in eggs from three locations in the San Joaquin Valley, and in egret eggs from Salton Sea.
Page, G. W., W. D. Shuford, J. E. Kjelmyr and L.
E. Stenzel, 1992. Shorebird numbers in wetlands of the Pacific
flyway: A summary of counts from April 1988 to January 1992. A
report of Point Reyes Bird Observatory, Stinson beach,
ABSTRACT: Since 1988 the Pacific Flyway Project has collected data on the importance of wetlands in the West to shorebirds. Although much is known about habitat needs and concentration areas of waterfowl in this region, the Flyway Project is the first large effort to gather comparable data on shorebirds -- the second most abundant group of birds in western wetlands. the bird use data will be combined with data on threats to wetlands to provide a picture of future prospects for shorebirds in the Flyway and to increase public awareness of the need to protect shorebirds by developing sound conservation and management strategies for their wetland habitats.
To date, the Flyway Project has identified 85 interior and 60 coastal wetlands that hold concentrations of greater than 1,000 shorebirds. Of these, 25 interior and 26 coastal sites hold greater than 10,000 shorebirds . In the interior, sites that hold greater than 100,000 shorebirds are the Lahontan Valley wetlands of western Nevada, Great Salt Lake in Utah, the Grasslands area of California's San Joaquin Valley, and the Salton Sea in southern California. Coastal sites that hold over 100,000 shorebirds are the Copper River and the Stikine River deltas in Alaska; the Fraser River delta in British Columbia; Puget Sound, grays Harbor and Willapa Bay in Washington; the Columbia River Estuary on the Washington-Oregon border; San Francisco Bay in California; and the mouth of the Colorado River and Laguna Ojo de Liebre in Mexico. San Francisco Bay is the only site shown by Flyway Project censuses to hold 1,000,000 shorebirds, though prior data indicate that both the Copper River delta and gays Harbor can at times hold comparable numbers of shorebirds. These results confirm that Pacific Flyway shorebirds concentrate at a relatively few wetlands, leaving large numbers of shorebirds at risk from threats at key sites.
Pacific Flyway Project data enables us to describe the species composition and pattern of seasonal use at each wetland and to map the broad geographic distribution patterns of all key species. the project also documented important links between wetlands in winter by uncovering the midwinter movement of Dunlins from coastal to interior wetlands in central California.
During the next two years the project will concentrate on completing its objective of obtaining three to five years of census data at all wetlands in the Pacific Flyway. Particular effort will be made to gather better data on shorebird use in California's vast Central Valley where large numbers of shorebirds use a variety of managed wetlands and agricultural habitats that compete for precious water supplies.
The Pacific Flyway Project prides itself on the value of its collaboration with private organizations, government agencies and individual volunteers. Only by such cooperation can adequate data be collected to ensure wise management of the wetlands upon which shorebirds depend.
Pemberton, J.R. 1927. The American Gull-billed
Tern breeding in California. Condor 29:253-258.
NOTES: Records of a brief visit to the Salton Sea in May 1927. Colonies of this tern found on islands at southern end, with total of about 500 occupied nests; first record of this species breeding away from the Atlantic coast. Terns fish at mouth of New River. Colonies also reported on these islands for White Pelican (450 occupied nests seen) and Caspian Terns (12 pairs). Records presence of numerous other species, including a Roseate Spoonbill "wading in shallow water in company with ibises and stilts;" this individual became the first spoonbill ever collected in California.
Platter, M.F. 1976. Breeding ecology of cattle
egrets, and snowy egrets at the Salton Sea, Southern California.
M.S. Thesis, San Diego State University. 122 pp.
ABSTRACT: Since about 1888, the Cattle Egret, Bubuleus ibis, has expanded its distributional range into South Africa, Australia, and North, Central, and South America. The species was first recorded breeding in the Imperial Valley, southern California, in 1969 at the New River delta on the Salton Sea. This colony also contained breeding Snowy Egrets, Egretta thula, and was intensively studied in 1974 from mid-March through September. Another colony developed in the New River delta during the breeding season, but failed due to predation, probably by raccoons. Estimated Cattle Egret populations varied during the breeding season from 750 to 6300 birds; the maximum population that was actively breeding was approximately 1480 birds. Estimated Snowy Egret active breeding population was approximately 308 birds; the population ranged from less than 50 to 500 birds. Evidence is presented for late summer movement of Cattle Egrets into the Imperial Valley.
The breeding season was arbitrarily divided into two parts, based on two general peaks in nesting activity. Snowy Egrets bred seven weeks after the first Cattle Egrets, during the second part of the season. Cattle Egret reproductive success was very low in the first part of the breeding season because of several periods of continuous high winds. Cattle Egret mean clutch size was 2.58 eggs and that for Snowy Egrets was 3.96 eggs. Both species showed a seasonal decrease in clutch size. Snowy Egrets had a significantly higher percentage of damaged eggs than did Cattle Egrets. Both species had the same percentage success in hatching and fledging, taking into consideration the larger Snowy Egret clutch. Cattle Egrets hatched 2.04 eggs and fledged 1.86 young per successful nest; Snowy Egrets hatched 3.10 eggs and fledged 2.90 young per successful nest. Cattle Egret nestling diet was, by volume, 53.0% insects, 18.5% spiders, 12.5% mice, and 16.0% of combined crawfish, earthworms, fish, and lizards. Snowy Egret diet was almost exclusively fish. Data from both hatched and broken eggs showed 17.3% thinning for Cattle Egrets and 18.8% for Snowy Egrets. The amount of thinning increases to 21.8% for Snowy Egrets when only broken eggs are considered. Residues of DDE, DDT, DDD, dieldrin, and PCB were found in Snowy Egret eggs, but only DDE was significantly correlated with decrease in eggshell thickness. Cattle Egret eggs were collected, but are not yet analyzed. During 1974, 132 juvenile and 5 adult Cattle Egrets were banded, wing tagged, and marked with picric acid dye. An additional 136 juvenile Cattle Egrets were banded and marked with dye, and 66 Snowy Egrets were banded.
Shuford W. and C.M. Hickey. 1996. A review of
the status of the White-Faced Ibis in winter in California.
Western Birds 27:169.
SUMMARY: Historical data on the distribution and abundance of the White-faced Ibis in winter in California are limited. Winter numbers declined to a low point in the 1970s, began to increase in the 1980s, and increased sharply in the early 1990s. Winter surveys in 1994-95 found at least 28,000 ibis in California, with the largest concentrations in the Sacramento Valley (2000-3000), the Grasslands of the San Joaquin Valley (8000), and the Imperial Valley (16,000). Additional surveys in 1995-96 estimated about 10,000 to 12,000 ibis in the greater Grasslands area. The wintering population in California likely increased as a byproduct of a westward shift in the abundance of breeding ibis, perhaps caused by a combination of flooding at Great Salt Lake, Utah, in the 1980s, similar shifts caused by drought conditions in the late 1980s to early 1990s, and improved habitat conditions on the breeding grounds in Oregon and northern California. Most ibis wintering in California forage in managed wetlands or agricultural fields, and private lands provide the majority of foraging habitat in all of the state's main wintering areas. Even in areas, such as the Imperial Valley, where ibis forage mostly in fields, managed wetlands are extremely important as nighttime roost sites. Ibis wintering in California remain at risk from accumulation of toxins, particularly in the Imperial Valley where they concentrate DDE residues that perisis in the soil from historical use. Population monitoring on the wintering grounds is needed to identify key wintering areas, assess trends in wintering populations, and pinpoint areas where wintering ibis may face risks to their survival.