Breeding Seabirds in California, Oregon, and Washington | ||
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 by Harry R. Carter National Biological Service David S. Gilmer National Biological Service Jean E. Takekawa U.S. Fish and Wildlife Service Roy W. Lowe U.S. Fish and Wildlife Service Ulrich W. Wilson U.S. Fish and Wildlife Service |
| More than two million seabirds of 29 species nest along the west coasts of California, Oregon, and Washington, including three species listed on the federal list of threatened and endangered species: the brown pelican (Pelecanus occidentalis), least tern (Sterna antillarum), and marbled murrelet (Brachyramphus marmoratus). The size and diversity of the breeding seabird community in this region reflect excellent nearshore prey conditions; subtropical waters within the southern California Bight area; complex tidal waters of Strait of Juan de Fuca and Puget Sound in Washington; large estuaries at San Francisco Bay, Columbia River, and Grays Harbor-Willapa bays; and the variety of nesting habitats used by seabirds throughout the region, including islands, mainland cliffs, old-growth forests, and artificial structures. | ||
| Breeding seabird populations along the west coast have declined since European settlement began in the late 1700's because of human occupation of, commercial use of, and introduction of mammalian predators to seabird nesting islands. In the 1900's, further declines occurred in association with rapid human population growth and intensive commercial use of natural resources in the Pacific region. In particular, severe adverse impacts have occurred from partial or complete nesting habitat destruction on islands or the mainland, human disturbance of nesting islands or areas, marine pollution, fisheries, and logging of old-growth forests (Ainley and Lewis 1974; Bartonek and Nettleship 1979; Hunt et al. 1979; Sowls et al. 1980; Nettleship et al. 1984; Speich and Wahl 1989; Ainley and Boekelheide 1990; Sealy 1990; Ainley and Hunt 1991; Carter and Morrison 1992; Carter et al. 1992; Vermeer et al. 1993). | ||
Methods |
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| Population status of breeding seabirds on the west coast has been measured primarily through the determination of and trends in population size, based on counts of birds and nests at nesting colonies (e.g., Sowls et al. 1980). At-sea surveys also have been used to approximate population sizes for breeding and nonbreeding populations and species as well as their foraging distribution alongshore and offshore (e.g., Briggs et al. 1987). Rather than just monitoring small plots of nests on a few accessible islands to determine status and trends, relatively accurate and standardized censuses of entire coastal seabird breeding populations (except for certain nesting areas of difficult-to-census species) have been conducted annually or periodically to determine the overall status of many species breeding on the west coast (Figs. 1-4). However, we have considered census accuracy, natural variability, trends at well-studied colonies (e.g., Farallon National Wildlife Refuge) and many other factors in assessing population status and trends. |
Fig. 1. Status and trends of breeding populations of storm-petrels, pelicans, and cormorants on the west coasts of California, Oregon, and Washington. Data for small inland populations of white pelicans and double-crested cormorants are not included. ND -- no data available; 0 -- no coastal nesting. Sources: CA (Hunt et al. 1979; Sowls et al. 1980; Carter et al. 1992); OR (Varoujean and Pitman 1979; R.W. Lowe, unpublished data); and WA (Speich and Wahl 1989; U.W. Wilson, unpublished data). Also see Carter et al. (in press) for double-crested cormorant. |
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Status and Trends |
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Storm-petrels (Hydrobatidae) |
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| Increasing numbers of Leach's storm-petrels (Oceanodroma leucorhoa) have been documented recently in Oregon (R.W. Lowe, USFWS, unpublished data), although this increase probably represents greater survey effort (Fig. 1). They have declined in northern California because of the loss of burrow-nesting habitats due to soil erosion and defoilation by nesting cormorants (Carter et al. 1992). Ashy storm-petrels (O. homochroa) have declined recently at the world's largest known colony at the South Farallon Islands, possibly because of high gull predation (W.J. Sydeman, Point Reyes Bird Observatory, unpublished data). This decline is of concern because the small world population of this species (fewer than 10,000 breeding birds) nests entirely in California. Greater numbers of ashy and black storm-petrels (O. melania) have been documented recently in southern California, although this probably reflects greater survey efforts (Carter et al. 1992). In Fig. 1, similar numbers of fork-tailed storm-petrels (O. furcata) are indicated over the past decade in Oregon and California because survey efforts confirmed very small numbers. Declines in California are suspected (Carter et al. 1992), but further work is required to establish trends. | ||
Pelicans (Pelecanidae) |
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| Brown pelicans have increased recently at the only two remaining colonies (West Anacapa and Santa Barbara islands) in the Channel Islands in southern California (Fig. 1), following severe pre-1975 declines primarily due to eggshell thinning from marine pollutants (Anderson et al. 1975; Anderson and Gress 1983; Carter et al. 1992; F. Gress and D.W. Anderson, University of California-Davis, personal communication). Breeding success is still low and limited recovery may involve immigration of birds out of Mexico. Concern exists for adverse effects of continuing low levels of marine pollutants, commercial fisheries, and the 1990 American Trader oil spill. Although the brown pelican has shown recent population increases, white pelicans have been extirpated from parts of interior California and have declined at inland colonies in northern California because of low reproduction related to water developments and drought (Carter et al. 1992; P. Moreno and D.W. Anderson, University of California-Davis, personal communication). Small colonies still exist at Sheepy Lake and Clear Lake in the Klamath Basin area. These conditions also exist at other inland areas in Oregon, Washington, and Nevada, but problems seem fewer farther east. | ||
Cormorants (Phalacrocoracidae) |
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| Double-crested cormorants (Phalacrocorax auritus) have increased dramatically in coastal regions of California and Oregon (Fig. 1) because of reduced human disturbance, reduced levels of marine pollutants in southern California, and recent use of artificial nesting areas in San Francisco Bay and Columbia River estuaries (Gress et al. 1973; Carter et al. 1992). They have not increased in Puget Sound because of high human disturbance and predation by bald eagles (Haliaeetus leucocephalus), which has caused colony abandonments (Henny et al. 1989; Speich and Wahl 1989; Carter et al. in press; U.W. Wilson, unpublished data). Declines have been reported at interior colonies in California, Oregon, and Washington due to water developments, human disturbance at colonies, and large-scale shooting of birds at hatcheries (during smolt releases) and at aquacultural facilities (Carter et al. in press; R.W. Lowe, unpublished data; R. Bayer, personal communication; P. Moreno, unpublished data). Brandt's and pelagic cormorant (P. penicillatus and P. pelagicus) populations have fluctuated in response to El Niño conditions (Ainley and Boekelheide 1990; Ainley et al. 1994). At the South Farallon Islands, these cormorants appear very sensitive to El Niño conditions, which result in quite poor reproduction and mortality of subadult and adult birds (Boekelheide and Ainley 1989; Ainley and Boekelheide 1990). Overall, numbers have remained stable or increased in most areas in the region (e.g., Carter et al. 1992), whereas these birds now occur at lower abundance than previously at the South Farallon Islands (Ainley et al. 1994). Numbers have increased in southern California, but the birds have suffered from gill-net and oil-spill mortality as well as human disturbance at colonies (H.R. Carter, unpublished data). | ||
Gulls, Terns, and Skimmers (Laridae and Rynchopidae) |
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| California gulls (L. californicus) have recently expanded from interior colonies to nest in San Francisco Bay (Fig. 2; Carter et al. 1992; P. Woodin, San Francisco Bay Bird Observatory, unpublished data). They face serious threats at inland colonies in interior California because of water developments. At the world's largest colony at Mono Lake, low water levels have resulted in the formation of land bridges to nesting islands, allowing access by coyotes (Canis latrans) in certain years (Jones and Stokes Associates 1993). Similar problems exist at other northern California colonies for many seabird and colonial waterbird species (W.D. Shuford, Point Reyes Bird Observatory, unpublished data). | ||
| The status of California gulls at inland colonies in Oregon and Washington is not well known. Status and trends of inland colonies of ring-billed gulls (L. delawarensis) in California, Oregon, and Washington are not known, although problems related to low water levels may occur at many colonies. Many thousands have nested recently in northern California (W.D. Shuford, unpublished data). Small numbers (< 500 breeding birds) also nest along the Washington coast (Speich and Wahl 1989). Small numbers (< 10 breeding birds) of Heermann's gulls (L. heermanni) nested in the early 1980's along the central California coast but none are known to do so now. Franklin's gulls (L. pipixcan) recently nested in small numbers (< 100 breeding birds) at Lower Klamath Lake, California, but their status in the region is not known. | ||
| Low thousands of Caspian, Forster's, least, and elegant terns (Sterna caspia, S. forsteri, S. antillarum, S. elegans) and black skimmers (Rynchops niger) now occur in the region through increases (especially along the southern California coast) due to colony protection and use of artificial nesting sites (Speich and Wahl 1989; Carter et al. 1992). Certain tern colonies have been eliminated or shifted (especially in San Francisco Bay) because of human disturbance and red fox (Vulpes vulpes) or other mammalian predation (P. Woodin, unpublished data). Overall, least tern colonies in California appear somewhat stable because of extensive management. They undoubtedly occur at lower than historical levels because of loss of nesting habitat, which continues to be threatened (Carter et al. 1992; R. Jurek, California Department of Fish and Game, personal communication). Low numbers (< 100 breeding birds) of arctic terns (S. paradisaea) have nested in coastal Washington in the past but not now (Speich and Wahl 1989). Small numbers (< 100 breeding birds) of gull-billed and royal terns (S. nilotica and S. maxima) recently colonized the southern California coast, although gull-billed terns have nested inland at the Salton Sea for a few decades. The status of black terns (Chlidonias niger) is not known. | ||
Alcids (Alcidae) |
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| Pigeon guillemot (Cepphus columba) populations have remained stable overall (Fig. 3), but major fluctuations have occurred in response to El Niño events at the South Farallon Islands and on the Oregon coast (Hodder and Graybill 1985; Ainley and Boekelheide 1990). A significant population and new nesting areas have been found recently in southern California, although higher numbers reflect both better survey techniques and population increases (Carter et al. 1992). Ancient murrelets (Synthliboramphus antiquus) nested on the Washington coast in the early 1900's but no longer do (Speich and Wahl 1989). Cassin's auklets (Ptychoramphus aleuticus) have declined at the largest known colony in the region at the South Farallon Islands, probably because of high gull predation and loss of burrow-nesting habitat from soil erosion (Carter et al. 1992; W.J. Sydeman, unpublished data). However, lower numbers also were found at Prince Island in southern California where numbers of nesting gulls are lower. Differences in survey techniques probably account for part of the lower numbers found recently, but other data on soil conditions, densities of nesting gulls, and gull predation support a decline at the South Farallon Islands (W.J. Sydeman, unpublished data). Hundreds also were killed in the 1984 Puerto Rican and 1986 Apex Houston oil spills (Ford et al. 1987; Page et al. 1990). |
Fig. 3. Status and trends of breeding populations of several alcids in California, Oregon, and Washington. Data for marbled murrelets and historical nesting by ancient murrelets are not included. ND -- no data available; 0 -- no coastal nesting. Sources: CA (Hunt et al. 1979; Sowls et al. 1980; Carter et al. 1992); OR (Varoujean and Pitman 1979; R.W. Lowe, unpublished data); and WA (Speich and Wahl 1989; U.W. Wilson, unpublished data). Also see Carter et al. (in press) for double-crested cormorant. |
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| Rhinoceros auklets (Cerorhinca monocerata) have increased throughout the region. Largest numbers occur at Protection and Destruction islands, but burrow occupancy has fluctuated widely between years (Wilson and Manuwal 1986; U.W. Wilson, unpublished data). The South Farallon Islands were recolonized after a 100-year absence in the early 1970's (Ainley and Lewis 1974) and reached saturation levels by the late 1980's (Carter et al. 1992; Ainley et al. 1994). Nesting has recently extended to the Channel Islands (Carter et al. 1992). Thousands of rhinoceros auklets were killed in the 1986 Apex Houston oil spill (Page et al. 1990). | ||
| The largest tufted puffin (Fratercula cirrhata) populations occur along the west coast of the Olympic Peninsula (Speich and Wahl 1989), but their status there is not well known. In Puget Sound, this species has declined substantially (U.W. Wilson, unpublished data). At small colonies in Oregon and California, their numbers appear stable (Carter et al. 1992; Fig. 3), despite impacts due to El Niño at the South Farallon Islands (Ainley and Boekelheide 1990; Ainley et al. 1994). They have recently recolonized southern California where they have not nested since the early 1900's (Carter et al. 1992). | ||
| Common murres (Uria aalge) are the dominant member of the breeding seabird community on the west coast but they have declined substantially in central California and Washington (Figs. 3, 4) because of the combined effects of high mortality from gill-net fishing and oil spills plus poor reproduction during intense El Niño events. In central California, large historical declines in the late 1800's and early 1900's almost led to the extinction of this population (Ainley and Lewis 1974). Population growth occurred, however, between the 1950's and the 1970's, producing about 230,000 breeding birds by 1980-82 (Takekawa et al. 1990). Over 70,000 murres were estimated to have been killed in gill nets in central California between 1979 and 1987, before heavy fishing restrictions were imposed in 1987 to stop mortality (Takekawa et al. 1990). Additional mortality (10,000+ murres) occurred during the 1984 Puerto Rican and 1986 Apex Houston oil spills (Ford et al. 1987; Page et al. 1990). At the South Farallon Islands, reproductive success was almost nil during intense El Niño events in 1983 and 1992 (Ainley and Boekelheide 1990; W.J. Sydeman, unpublished data). Because of these and other factors, the central California population declined by over 60% from 1982 to 1989 and has not recovered (Fig. 4; Takekawa et al. 1990; Carter et al. 1992; Ainley et al. 1994; H.R. Carter, unpublished data). | ||
| In Washington, murre numbers crashed during the 1982-83 El Niño (Wilson 1991), although there was heavy mortality from gill nets at this time; mortality from gill nets still continues in Puget Sound. In addition, certain colonies have been disturbed by low-flying aircraft, especially near military bases. Numbers of breeding murres in Washington are lower than indicated in Figs. 3 and 4 because many birds counted in colonies in recent years (and used to derive estimates) do not appear to be breeding (U.W. Wilson, unpublished data). Significant mortality occurred during the 1984 Arco Anchorage, 1988 Nestucca, and 1991 Tenyo Maru oil spills. In the Nestucca spill alone, about 30,000 murres were estimated to have died (Ford et al. 1991). The Washington population of murres has been almost extirpated over the last decade and has not recovered. | ||
| Marbled murrelets probably have declined substantially throughout the region largely because of the direct loss of most (90%-95%) of their old-growth forest nesting habitat to large-scale logging since the mid-1800's (Carter and Morrison 1992; FEMAT 1994). About 10,000-20,000 birds remain. In addition, hundreds of murrelets have been killed in gill nets and oil spills in central California, Puget Sound, and off the Olympic Peninsula (Carter and Morrison 1992; H.R. Carter, unpublished data). Murrelets appear to have very low reproductive rates (based on nests examined and at-sea counts of juveniles), probably because of high avian nest predation in fragmented forests and possibly lower breeding success during intense El Niño events. This species was listed as threatened in California, Oregon, and Washington in 1992, and is being considered carefully with regard to the future of old-growth forests and the timber industry in this region. Small populations in California, Oregon, and southwestern Washington are isolated and susceptible to extinction from various potential disturbances in the future. | ||
| The Xantus' murrelet (Synthliboramphus hypoleucus) persists in very low numbers (2,000-5,000 breeding birds) only in southern California. Numbers breeding at the largest colony at Santa Barbara Island probably have declined between the mid-1970's and 1991 (Fig. 3; Carter et al. 1992). The decline may have occurred because of many factors, including census differences. Poor reproduction, however, has occurred because of high levels of avian and mammalian predation and has probably led to this decline. Other smaller colonies may disappear because of mortality from oil spills from offshore platforms in Santa Barbara Channel and oil tanker traffic into Los Angeles harbor and other factors. Larger numbers of nesting birds are now suspected in southern California (H.R. Carter, unpublished data). A significant portion of the small world population of this species nests in southern California while the remainder nests on the northwest coast of Baja California, Mexico. This candidate species may be considered for federal and state listing in the near future. | ||
Future Efforts |
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| Because of the continuing decline of and threats to seabirds on broad regional and local levels along the west coast, efforts to determine status and trends of seabirds must be extended beyond current levels. Long-term efforts must be shared among many federal and state agencies, universities, and private groups, including (1) the development of a coordinated long-term monitoring and research program, including data-base development and maintenance; (2) extending monitoring to all coastal and inland areas and species; (3) developing new methodologies for surveying nocturnal species of murrelets, auklets, and storm-petrels; (4) conducting studies of specific conservation problems such as loss of nesting habitats (e.g., old-growth forests), gill-net mortality (e.g., Puget Sound), oil-spill mortality, human disturbance, water developments, and agricultural practices; (5) restoring lost or depleted seabird colonies and habitats; and (6) examining the possible long-term effects of human fisheries and global climate change on seabird prey resources and nesting habitats. | ||
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National Biological Service California Pacific Science Center 6924 Tremont Rd. Dixon, CA 95620 |
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| References | |
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Ainley, D.G., and R.J. Boekelheide, eds. 1990. Seabirds of the Farallon Islands: ecology, dynamics, and structure of an upwelling-system community. Stanford University Press, Stanford, CA. 450 pp. Ainley, D.G., and G.W. Hunt, Jr. 1991. The status and conservation of seabirds in California. Pages 103-114 in J.P. Croxall, ed. Seabird status and conservation: a supplement. International Council of Bird Preservation Tech. Bull. 11. Ainley, D.G., and T.J. Lewis. 1974. The history of Farallon Island marine bird population, 1854-1972. Condor 76:432-446. Ainley, D.G., W.J. Sydeman, S.A. Hatch, and U.W. Wilson. 1994. Seabird population trends along the west coast of North America: causes and extent of regional concordance. Studies in Avian Biology 15:119-133. Anderson, D.W., and F. Gress. 1983. Status of a northern population of California brown pelicans. Condor 85:79-88. Anderson, D.W., J.R. Jehl, R.W. Risebrough, L.A. Woods, L.R. DeWeese, and W.G. Edgecomb. 1975. Brown pelicans: improved reproduction off the southern California coast. Science 190:806-808. Bartonek, J.C., and D.N. Nettleship, eds. 1979. Conservation of marine birds of northern North America. U.S. Fish and Wildlife Service, Wildlife Res. Rep. 11. 319 pp. Boekelheide, R.J., and D.G. Ainley. 1989. Age, resource availability, and breeding effort in Brandt's cormorant. Auk 106:389-401. Briggs, K.T., W.B. Tyler, D.B. Lewis, and D.R. Carlson. 1987. Bird communities at sea off California: 1975 to 1983. Studies in Avian Biology 11. 74 pp. Carter, H.R., and M.L. Morrison, eds. 1992. Status and conservation of the marbled murrelet in North America. Proceedings of a 1987 Pacific Seabird Group Symposium. Proceedings of the Western Foundation of Vertebrate Zoology 5. Camarillo, CA. 134 pp. Carter, H.R., G.J. McChesney, D.L. Jaques, C.S. Strong, M.W. Parker, J.E. Takekawa, D.L. Jory, and D.L. Whitworth. 1992. Breeding populations of seabirds in California, 1989-1991. Vol 1. U.S. Fish and Wildlife Service, Dixon, CA. [Unpublished final report.] Carter, H.R., A.L. Sowls, M.S. Rodway, U.W. Wilson, R.W. Lowe, F. Gress, and D.W. Anderson. Status of the double-crested cormorant on the west coast of North America. Colonial Waterbirds. In press. Ford, R.G., G.W. Page, and H.R. Carter. 1987. Estimating mortality of seabirds from oil spills. Pages 747-751 in Proceedings of the 1987 Oil Spill Conference. American Petroleum Institute, Washington, DC. Ford, R.G., D.H. Varoujean, D.R. Warrick, W.A. Williams, D.B. Lewis, C.L. Hewitt, and J.L. Casey. 1991. Seabird mortality resulting from the Nestucca oil spill incident winter 1988-89. Ecological Consulting Incorporated, Portland, OR. [Unpublished report.] Forest Ecosystem Management Assessment Team (FEMAT). 1994. Forest ecosystem management: an ecological, economic, and social assessment. U.S. Departments of Agriculture and Interior, Washington, DC. |
Gress, F., R.W. Risebrough, D.W. Anderson, L.F. Kiff, and J.R. Jehl, Jr. 1973. Reproductive failures of double-crested cormorants in southern California and Baja California. Wilson Bull. 85:197-208. Henny, C.J., L.J. Blus, S.P. Thompson, and U.W. Wilson. 1989. Environmental contaminants, human disturbance and nesting of double-crested cormorants in northwestern Washington. Colonial Waterbirds 12:198-206. Hodder, J., and M.R. Graybill. 1985. Reproduction and survival of seabirds in Oregon during the 1982-83 El Niño. Condor 87:535-541. Hunt, G.L., R.L. Pitman, M. Naughton, K. Winnett, A. Newman, P.R. Kelly, and K.T. Briggs. 1979. Reproductive ecology and foraging habits of breeding seabirds. Pages 1-399 in Summary of marine mammal and seabird surveys of the southern California Bight area 1975-1978. Vol. 3--Investigators' reports. Part 3. Seabirds--Book 2. University of California-Santa Cruz. For U.S. Bureau of Land Management, Los Angeles, CA. Contract AA550-CT7-36. [Unpublished report.] Jones and Stokes Associates. 1993. Environmental impact report for the review of Mono Basin water rights of the City of Los Angeles. Draft. May. (JSA 90-171.) Prepared for California State Water Resources Control Board, Division of Water Rights, Sacramento, CA. Nettleship, D.N., G.A. Sanger, and P.F. Springer, eds. 1984. Marine birds: their feeding ecology and commercial fisheries relationships. Proceedings of the Pacific Seabird Group Symposium. Canadian Wildlife Service Spec. Publ., Ottawa, Ontario. 220 pp. Page, G.W., H.R. Carter, and R.G. Ford. 1990. Numbers of seabirds killed or debilitated in the 1986 Apex Houston oil spill in central California. Pages 164-174 in S.G. Sealy, ed. Auks at sea. Proceedings of an International Symposium of the Pacific Seabird Group. Studies in Avian Biology 14. Sealy, S.G., ed. 1990. Auks at sea. Proceedings of an International Symposium of the Pacific Seabird Group. Studies in Avian Biology 14. 180 pp. Sowls, A.L., A.R. DeGange, J.W. Nelson, and G.S. Lester. 1980. Catalog of California seabird colonies. U.S. Fish and Wildlife Service, FWS/OBS 37/80. 371 pp. Speich, S.M., and T.R. Wahl. 1989. Catalog of Washington seabird colonies. U.S. Fish and Wildlife Service, Biological Rep. 88(6). 510 pp. Takekawa, J.E., H.R. Carter, and T.E. Harvey. 1990. Decline of the common murre in central California, 1980-1986. Pages 149-163 in S.G. Sealy, ed. Auks at sea. Proceedings of an International Symposium of the Pacific Seabird Group. Studies in Avian Biology 14. Varoujean, D.H., and R.L. Pitman. 1979. Oregon seabird survey 1979. U.S. Fish and Wildlife Service, Portland, OR. Unpublished report. Vermeer, K., K.T. Briggs, K.H. Morgan, and D. Siegel-Causey, eds. 1993. The status, ecology, and conservation of marine birds of the North Pacific. Proceedings of a Pacific Seabird Group Symposium. Canadian Wildlife Service Spec. Publ. Ottawa, Ontario. 263 pp. Wilson, U.W. 1991. Responses of three seabird species to El Niño events and other warm episodes on the Washington coast, 1979-1990. Condor 93:853-858. Wilson, U.W., and D.A. Manuwal. 1986. Breeding biology of the rhinoceros auklet in Washington. Condor 88:143-155. |
