occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) BREEDING: coastally along Pacific coast from southern Alaska (very local, Prince William Sound and Hazy Island near Coronation Island) and Vancouver Island and Washington (small, local populations) south to Baja California, including Pacific coastal islands of Baja; local on some islands in the Gulf of California (San Pedro Martir, Salsipuedes, and Roca Blanca) (Johnsgard 1993). NON-BREEDING: mostly near nesting areas. Common to very abundant as a non-breeder in southern British Columbia (Campbell et al. 1990). Extends north to Prince Williams Sound, Alaska and to southern Baja California.

Length: 89 cm

Weight: 2103 grams

• Terrestrial
• Marine

Comments: Mainly inshore coastal zone, especially in areas having kelp beds; also around some offshore islands; less commonly, inshore on brackish bays; in winter, mostly around sheltered inlets and other quiet waters (Palmer 1962, AOU 1983, Johnsgard 1993). Typically nests on flat or gently sloping surfaces on tops of rocky islands along coast, favoring protected leeward sides of islands; frequently nests with other sea birds; may sometimes use wider ledges of mainland cliffs. Nest is built on ground by both sexes, may be re-used in subsequent year.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Resident throughout year near nesting areas, but ranges more widely when not breeding. Post-breeding dispersal from colonies on west coast of United States occurs in July and August as thousands move north to the waters of southern British Columbia and Puget Sound; a gradual movement southward begins in September and October, but at least 10,000 to 15,000 overwinter in Puget Sound, the Strait of Georgia, and Juan de Fuca Strait (Campbell et al. 1990, Johnsgard 1993).

Comments: Feeds on small saltwater fishes, especially those at or near the bottom but also those throughout the water column (schooling and nonschooling species), and squid; primarily on fishes of no commercial value. Also feeds on crabs and shrimps. In the north, feeds more often over sand or mud bottoms than does the pelagic cormorant. See Johnsgard (1993) for further information.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: Colonial nester along the Pacific Coast of North America. Sixty-six major colonies identified by Wallace and Wallace (1998).

10,000 - 100,000 individuals

Comments: Boekelheide et al. (1990, cited in Wallace and Wallace 1998) estimated worldwide population at 75,600. Previously, breeding population along coast of California, Washington, and Oregon was estimated at about 80,000 (mostly in California, especially Farallon Islands; Spendelow and Patton 1988); fewer than 50 pairs in Alaska (Lensink 1984) and small numbers in British Columbia (Vermeer and Sealy 1984). In California, at least 13 colonies include at least 1000 birds; average nesting population on Farallon Islands was 16,000 in the 1970s and 1980s. Perhaps 10,000-11,000 pairs along Pacific coast of Mexico (DeLong and Crossin, see Johnsgard 1993).

Gathers in flocks in feeding areas. Male establishes territory in immediate area of nest. In winter in California, made 55-km round trips between roost and feeding area (see Johnsgard 1993). Increased sea surface temperatures, such as those associated with El Nino events, were correlated with decreases in nesting populations in Washington (Wilson 1991). Gulls commonly prey on eggs and chicks.

Egg laying occurs mainly in June in British Columbia, late May and June in northern California, mid-April to early July in central California, and late February to mid-June in southern California (Johnsgard 1993). Both parents, in turn, incubate 3-6 (usually 3-4) eggs. Incubation lasts 28-32 days. Nestlings altricial. Fledging occurs at about 40-42 days. Single brooded but some lay replacement clutch if first clutch is lost. On Farallon Islands, females first bred at modal age of 2 years (mostly 2-5 years), males at 4 years (mostly 3-5 years); mate fidelity is low; the most successful individuals fledged 10-20 chicks over their lifetime; all adults skipped breeding at least one year during their reproductive lifetime; food availability affected many reproductive parameters; reproductive success varied considerably among years (Boekelheide and Ainley 1989).

Canada

Rounded National Status Rank: N1B,N4N : N1B: Critically Imperiled - Breeding, N4N: Apparently Secure - Nonbreeding

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Population stable and increasing in some parts.

Global Short Term Trend: Relatively stable (=10% change)

Comments: Colonies vary annually making trend estimates difficult. In Oregon, population increased 1988-1994. In California, at least 20 colonies increased from 13 pairs in 1975-1980 to over 500 pairs in 1989-1991. Population in northern California lower in 1989-1991 than in 1975-1980; increased in southern California during the same period (Carter et al. 1992, cited in Wallace and Wallace 1998). On Farallon Islands, California, increased to about 11,900 pairs in 1974 and estimated at 8,451 pairs in 1989 (Boekelheide et al. 1990). Christmas Bird Count (CBC) shows surveywide increasing trend (3.0 percent annual average change; N = 91) for 1959-1988. Positive trend in British Columbia (18.6 percent annual change; N = 24) and Washington (14.0 percent annual average change; N = 19). Only negative trend in California (-5.3 percent annual change; N = 41; Sauer et al. 1996).

Degree of Threat: C : Not very threatened throughout its range, communities often provide natural resources that when exploited alter the composition and structure over the short-term, or communities are self-protecting because they are unsuitable for other uses

Comments: PESTICIDES: DDE, DDT, PCB, EDDT, dieldrin, oxychlordane, heptachloroepoxide, mercury, selenium, PCDDs, PCDFs, and EPCB found in eggs; not correlated with eggshell thining or mortality (Wallace and Wallace 1998). Chick with deformed bill typical of high concentrations of pollutants found on Farallon Island, California (Hobson and Carter 1988, cited in Wallace and Wallace 1998). Regional variation of DDT and DDE residue levels found in prey. Deaths of some captive birds were attributed to high concentrations of DDT in food source. OILING: Small numbers died after oil spills. Oiling damages plumage that results in hypothermia or waterlogging. Ingested oil has variety of lethal and non-lethal effects. Over 50 percent of recovered birds 1971-1985 were suspected to have died of oiling. Numbers may be higher due to tendency of this species to sink. FISHING NETS: Mortality from coastal fishing nets may have exceeded sustainable levels in Monterey, California in early 1980s (King 1984 cited in Wallace and Wallace 1998). HABITAT: Local declines or disappearance due to loss of habitat. DISTURBANCE: Vulnerable to disturbance by boats, low-flying aircraft, dogs, or humans especially during incubation period. Mortality has resulted from military bombing practice and missile tests on some California Channel Islands. Flushing adults may break eggs and increase chance of nest predation. Repeated disturbance may cause total colony desertion. Local decline attributed to disturbance caused by collection of common murre (Uria aalge) eggs from 1850s to 1900s (Ainley and Lewis 1974, cited in Wallace and Wallace). Incidental injury and death reported by sportsfisherman (Wallace and Wallace 1998). PREDATION: Nest predators include western gull (Larus occidentalis), Heerman's gull (LARUS HERMANNI), northwestern crow (Corvus caurinus), common raven (Corvus corax). Western gull may prey on deserted eggs or young. Rats (Rattus spp.) known to take eggs on Isla San Esteban (Wallace and Wallace 1998). EL NINO-SOUTHERN OSCILLATION (ENSO): Reduced reproductive output during and after periods of ENSO. ENSO occurs when warm waters prevail causing food levels to decline. Will abandon nest sites mid-season if food sources decline. In 1983, all nests were abandoned at two Oregon colonies and at least 49 percent of nests failed or had reduced fledgling success at another colony (Hodder and Graybill 1985, cited in Wallace and Wallace 1998). Periods of high mortality also attributed to food shortages related to ENSO. Additional reported deaths due to poisoning after ingesting fish affected by red tide (the dinoflagellate Gymnodinium breve) or northern anchovies containing valves of the diatom Pseudonitzschia australis. Also, one death reported to lodging of a plainfin midshipman in the throat. COMPETITION: Expanding fisheries industry and increase in the California Sea Lion (Zalophus californianus) populations may be suppressing recovery from effects of 1982-1983 EL NINO SOUTHERN OCCILATION (ENSO). Expansion of groundfish fisheries may reduce food availability to cormorants (Wallace and Wallace 1998). PARASITISM: Not known to occur.

Global Protection: Many to very many (13 to >40) occurrences appropriately protected and managed

Comments: Most nesting habitat in Oregon protected by three wildlife refuges. Surrounding waters, however, are not protected. In California, nearly all coastal islands and rocks are protected and use of gill nets has been restricted. Many Gulf of California islands are protected as wildlife refuges (Jehl 1973, cited in Wallace and Wallace 1998). Several colonies on the Pacific Coast of Baja California protected by island residents or established as a biosphere reserve. A 91 meter exclusion zone was established in 1993 around Farallon Island, California effective during the breeding season. A zone of 152 meters was established around Three Arch Rocks National Wildlife Refuge in 1994. Receives legal protection from egging and from shooting.

Comments: See Siegel-Causey (1988) for analysis of relationships within family. Siegel-Causey (1988) proposed removing this species from the genus Phalacrocorax and placing it in the genus Compsohalieus; DeBenedictus (1989) concluded that the taxonomic ranks of many groups recognized by Siegel-Causey (1988) are inflated and inconsistent with other taxonomic data.