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Double-crested Cormorant

Phalacrocorax auritus

Order:
Suliformes
Family:
Phalacrocoracidae
Sections

Distribution, Migration and Habitat

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Figure 1. Distribution of the Double-crested Cormorant.

This species also winters in Bermuda in small numbers, and winters locally south to the dashed line. See text for details.

Enlarge
eBird range map for Double-crested Cormorant

Generated from eBird observations (Year-Round, 1900-2017)

Distribution in the Americas

eBird data provide detailed looks at the range of this species throughout the year: eBird Year-round Range and Point Map for Double-crested Cormorant.

Breeding Range

Widely distributed in North America, but not beyond (Figure 1, Figure 10); currently expanding, but mostly within historical range (Hatch 1995a). Breeding cormorants are most numerous in the outer parts of this range, in 5 main zones: (1) Alaska, (2) Pacific Coast from s. British Columbia to n. Mexico, (3) Canadian and U.S. interior, (4) Atlantic Coast from Newfoundland to New York, and (5) Florida and the w. Caribbean. For (1) and (2), see Carter et al. 1995b. Recent expansion has blurred boundaries for (3), (4), and (5).

Alaskan population breeds at Nunivak I. (60°N) and se. Bering Sea and from e. Aleutian Is. to se. coast, including Kodiak I. (Carter et al. 1995b, U.S. Fish and Wildlife Service 1999a), and inland to Lake Louise, AK. First nest in Yukon Territory confirmed in 1998 at Lake Laberge (Bain and Shanahan 1998); remains a rare breeder there (Sinclair et al. 2003).

Pacific population breeds between s. British Columbia and Sinaloa, Mexico. In these coastal areas, Double-crested Cormorant is generally outnumbered by other cormorants. Smaller numbers nest inland, without other cormorants, except in Mexico where the Neotropic Cormorant occurs. Breeds in the Strait of Georgia in s. British Columbia and n. Washington (Campbell et al. 1990b, Smith et al. 1997). In Washington and Oregon, most breeders are coastal, with small numbers inland, occasionally along the lower Columbia and n. Willamette rivers. East of the Cascades, colonies are widely scattered and locations shift in response to fluctuating water conditions, but most occur in Klamath, Lake, and Harney Cos., OR, and Grant Co., WA (Gilligan et al. 1994, Smith et al. 1997; Courtot et al. 2012)..

In California, most individuals have nested coastally, especially from Cape Mendocino northward, and in lakes and marshes of Siskiyou, Modoc, and Lassen Cos.; small numbers in San Francisco Bay, Central Valley, and lower Colorado River; declining numbers on the Salton Sea; and very locally elsewhere (Small 1994).

In Mexico, breeds along the Pacific coast of Baja California, on islands in the Gulf of California, and locally inland in Durango and se. Sonora, and on the coast of central Sonora (Howell and Webb 1995, Russell and Monson 1998). Records from Sinaloa date from the 1970s (Carter et al. 1995b).

In the interior of the continent, northern limits of breeding may be determined by the short season and the distribution of productive lakes: from the southern boreal forest in n. Alberta, Saskatchewan, and Manitoba (http://www.birdatlas.mb.ca/mbdata/maps.jsp?lang=en), through central Ontario (primarily along the Great Lakes); James Bay, where a single colony was reported from Rupert Bay (Tymstra 1997, Weseloh 2007) and sw. Quebec (Gauthier and Aubrey 1996), south to central Utah, central Colorado, w.-central Nebraska, se. South Dakota, w.-central Minnesota, ne. Iowa, central Wisconsin (http://www.uwgb.edu/birds/wbba/species/maps/DCCO.htm, and the n. Lower Peninsula of Michigan (http://www.mibirdatlas.org/Portals/12/MBA2010/DCCOaccount.pdf).

Range extends west to sw. Idaho and east along the Great Lakes to the lower St. Lawrence River (eBird data). Also breeds locally elsewhere in s. Ontario, in sw. Quebec (Gauthier and Aubry 1996b), central Kansas (confirmed breeding at only 3 sites; Busby and Zimmerman 2001), s. New Mexico (lower Rio Grande and Pecos River valleys, but no confirmed nesting in recent decades Hubbard 1978c, http://www.pwrc.usgs.gov/bba/index.cfm?fa=explore.ResultsBySpecies ), and irregularly elsewhere within the central North American interior. In Texas, scattered breeding in recent decades, primarily in eastern regions, well documented by R. Telfair (http://txtbba.tamu.edu/species-accounts/double-crested-cormorant/).

On the Atlantic Coast, breeds almost entirely from s. Newfoundland, the north shore of the Gulf and the estuary of the St. Lawrence, Anticosti I., Magdalen Is., and south to New York City. Widespread in the coastal Maritime Provinces (http://www.mba-aom.ca/jsp/map.jsp?lang=en).

Now expanding south into the mid-Atlantic states (see Historical changes, below). Inland nesting now well established on Lake Champlain (Vermont/New York), and by small numbers elsewhere—in Quebec, Maine, Connecticut, Pennsylvania, Maryland (Brinker 2010), Virginia, and the Carolinas.

In the Southeast, resident throughout Florida except panhandle (Stevenson and Anderson 1994b, Hatch 1995a). Generally rare as a breeder in the southeast (Georgia, Alabama, Mississippi, Louisiana, and Arkansas; see Reinhold et al. 1998, Wires and Cuthbert 2006).

Scattered residents breed in Cuba, where colonies are reported in some small keys off northern coast, from Bahía de Cadiz to Cayo Santa María; also in s. Havana province and Golfo de Guacanayabo (O. Garrido and A. Kirkconnell pers. comm.). In the n. Bahamas, known as uncommon resident, nesting confirmed on San Salvador, Long I., and Eleuthera (Connor and Lofkin 1985, Watson et al. 1991). Also nests on coast of n. Yucatán Peninsula (Mexico) and n. Belize (Howell and Webb 1995, Raffaele et al. 1998).

Nonbreeding Summer Range

Found mostly within limits of its wide breeding range, but occurs farther from breeding colonies, even to elevations of > 2,000 m, as at Crater Lake, OR (Gilligan et al. 1994). Uncommon in the Queen Charlotte Is., BC. Some remain in wintering areas (e.g., ne. Mexico [Howell and Webb 1995], and Florida, where indistinguishable from residents, and Mississippi). In late summer, likely to disperse beyond breeding range—e.g., to Great Slave Lake, Northwest Territories.

Winter Range

Figure 12. On the Pacific Coast, including Alaska, chiefly resident; some dispersal northward, but more southward, especially from inland, as far as Sinaloa, Mexico. In British Columbia, birds wintering north of breeding areas likely include migrants from Alaska. Also winters inland along the Columbia River of Washington and Oregon, throughout the near coastal counties of Oregon and California, throughout the Central Valley of California, and along the lower Colorado River (Christmas Bird Count [CBC] data). These patterns are not based on marked individuals.

Individuals breeding in the interior of the continent and on the Atlantic Coast are strongly migratory, most wintering coastally from N. Carolina to the w. Gulf of Mexico, with smaller numbers north to New Hampshire (Root 1988b, Sauer et al. 1996c, Davenport 1998, CBC records). Also winters along the Gulf Coast of Mexico from Tamaulipas south to the Yucatán Peninsula and Belize. Banded birds recovered from as far as Quintana Roo, Mexico. Numerous band recoveries show that mixing occurs of birds from across wide breeding range east of Rocky Mtns. (Dolbeer 1991, Hatch 1995a), as well as overlap with residents. However, there is evidence of a migratory divide between the interior and Atlantic coast meta-populations (Guillaumet et al. 2011).

North American birds also winter in the n. Bahamas, with occasional sightings in Puerto Rico and the n. Lesser Antilles (Raffaele et al. 1998), and south to Cuba. Banding recoveries include 12 in Cuba (banded S. Dakota–Quebec), 1 in n. Bahamas. On Bermuda, small numbers have wintered since about 1980 (Amos 1991).

Significant numbers occur in winter at inland lakes, rivers, and impoundments; regularly winters inland from the Atlantic Coast along major rivers to se. Pennsylvania, central Maryland, and throughout the lower coastal plains of Virginia and the Carolinas. Also winters inland from the Gulf Coast (especially along the Mississippi and other rivers) north to central Georgia, n. Tennessee, sw. Indiana, s. Illinois, n. Arkansas, e. Kansas, the eastern half of Oklahoma, Texas (except for panhandle); in ne. Mexico in Nuevo León, Tamaulipas, and n. Veracruz; and along the Rio Grande and Pecos rivers of s. New Mexico and w. and s. Texas (CBC data, Howell and Webb 1995). To the north, small numbers are increasingly observed on CBCs in coastal New England, the Maritime Provinces, the Great Lakes, and the prairies.

Other populations breeding in Florida, Mexico, Cuba, and the Bahamas are resident. In southern areas, influx of migrants is added to residents, but no information is available on possible differences in habitat use. For possible sex differences in wintering areas, see Habitat, below.

Distribution Outside the Americas

Vagrants reported from the Azores in 1991, England in 1989 (BOURC 1993).

Nature of Migration

Variable; birds nesting in the interior and on the Atlantic Coast (P. a. auritus) are highly migratory; all age groups migrate. Immature birds arrive later in spring but are not known to occupy different ranges. In other areas, mostly resident within breeding range, and very little is known of migratory habits. In Florida and the Caribbean, P. a. floridanus is reported to be resident, but withdraws from the Carolinas in winter (Bent 1922). Its breeding range overlaps with migration and wintering areas of P. a. auritus, from which it is indistinguishable in the field.

In the Bahamas, P. a. heuretus is probably resident (Watson et al. 1991). The more northerly populations of P. a. cincinatus (in Alaska) may migrate south to s. British Columbia, especially the outer coast (Campbell et al. 1990b, Johnsgard 1993) and Washington, but specific data are lacking. In Mexico and California, coastal and southern areas receive an influx of birds in fall, probably P. a. albociliatus from inland or farther north. Birds banded in British Columbia are encountered south to s. California.

A change in wintering areas (and migration routes) is suggested by recoveries of cormorants banded in S. Dakota; from Louisiana in 1930 to Texas and Mexico in 1960s (Drewlen and Fredrickson 1969). King et al. (2010) indicated a potential shift inland for wintering cormorants in the Southeast due to the expansion of catfish aquaculture in the region.

Timing and Routes of Migration

Spring

Some birds leave the Gulf of Mexico as early as Feb. They follow the Atlantic coastline or river systems, as well as going overland. Earliest individuals reach Oklahoma and Virginia by 4–5 Mar (Sutton 1967b, Kain 1987b); Massachusetts, s. Great Lakes, Minnesota, S. Dakota, and s. Idaho by late Mar-early Apr; upper Great Lakes by early to mid-Apr; coastal Maine, Alberta, and Saskatchewan by mid- to late Apr. First adults arrive at colonies in e. Lake Ontario when ice breakup is well advanced but large areas of pack ice are usually still present (DVW). Similarly, first arrivals at North Channel (Lake Huron) may be confined to river or creek mouths that form the only open water (S. Elliott pers. comm.). Peak spring migrations occur 3–4 wk later, in Missouri in third week of Apr (Robbins and Easterla 1992), in Massachusetts in late Apr.

Cormorants marked with satellite telemetry on their wintering grounds in Mississippi departed for spring migration between 26 Mar and 12 May, with adult cormorants departing earlier for spring migration than immatures (King et al. 2012a). Mean duration of migration was 12 d, with marked cormorants traveling an average of 70 km/d (King et al. 2012a).

Records of migrants in large numbers en route are rarely published, but a very large passage was reported on 24 Apr 1926, when “100,000–1,000,000” cormorants passed La Crosse, WI, flying up the Mississippi River (Robbins 1991). From banding recoveries, Dolbeer (Dolbeer 1991) concluded that first-year birds return north about a month later than older birds.

On the Pacific Coast, migration is poorly known because some individuals are resident year-round. Migrants leave Oregon in Mar (Gilligan et al. 1994). In British Columbia, migration period is mid-Mar–late May, with heaviest movements late Apr–early May (Campbell et al. 1990b). In interior Oregon, migrants arrive Feb–Mar. In California, arrive at Farallon Is. early Mar–mid-Apr (Ainley and Boekelheide 1990).

Fall

Autumn migration is essentially the reverse of spring migration, but movements are well under way before open water becomes limiting. Earliest autumn migrants appear to reach wintering grounds faster than they reached breeding grounds in spring, although overall timing is more protracted. The average departure date for fall migration of satellite-marked cormorants from various locations in their breeding range was 1 Oct (range, 17 Aug to 25 Oct, n = 8; see King et al. 2012). Females may have an earlier mean departure date (12 Sep [n = 10]) than males (7 Oct [n = 16]; see Scherr et al. 2010).

Cormorants marked from a colony managed for reduction in numbers by egg-oiling had a mean departure date of 6 Sep (range 12 Jul to 29 Oct, n = 24; see Dorr et al. 2012d), suggesting that egg-oiling induced nest failure may result in slightly earlier migration. Several juveniles banded in Michigan have been recovered on the Mississippi River from s. Minnesota to s. Missouri by late Jul (J. Ludwig unpubl.). More usually, migration is evident on Canadian prairies by mid- to late Aug; by then first migrants are on the upper Mississippi River (Kirsch 1997) and in Ohio, Massachusetts, Virginia, and even Texas (Oberholser 1974c).

By September, migration is well under way throughout the range. From Lake Champlain (Vermont/New York), all individuals depart within a few days in late September (D. Capen pers. comm.). Several areas report peak numbers of transients in Oct (Massachusetts and Rhode Island: first half; Minnesota: third week). Very few descriptions available of what must be large movements both down the Mississippi River/Flyway and out of the Great Lakes: Two reports from 1940s describe 9,500 and 15,000 birds, respectively, passing Havana, IL, on single days in early Oct (Mills et al. 1966). Near Rochester, NY, hundreds are seen each year flying westward along the southern shore of Lake Ontario (B. Ewald unpubl.).

Most banded migrants are recovered in Oct and Nov (Dolbeer 1991). Mean duration of fall migration of satellite-marked cormorants from a colony in e. Lake Ontario was 34 d (range 2-110 d, n = 19; see Dorr et al. 2012d). Mean duration of fall migration of satellite-marked cormorants from a colony in n. Lake Huron was 41 d (range 6-87 d; see Scherr et al. 2010). The mean migration distance that birds traveled from n. Lake Huron to their winter location was 2,060 km (Scherr et al. 2010). The greatest daily movement was 343 km/d by a female; however, males and females did not differ (Scherr et al. 2010).

Patterns of coastal migration in New England, described by Nisbet and Baird (Nisbet and Baird 1959), continue with much greater numbers in 1990s (JJH). Flocks are generally observed along the coast, except where they fly overland to bypass Cape Ann, MA, and again for Cape Cod. Small flocks appear in mid-Aug, but most migration has been observed 25 Sep–17 Oct. Individuals arrive in wintering areas Sep–Nov. Some fly across open ocean (species now winters regularly in Bermuda), but is rarely seen during cruises in search of pelagic seabirds.

There is evidence of a migratory divide and migratory connectivity for the Atlantic and Mississippi flyways (Scherr et al. 2010, Dorr et al. 2012d, Guillaumet et al. 2012). Cormorants breeding west of central Lake Erie tend to migrate west of the Appalachians and congregate in the lower Mississippi valley; eastern breeding birds migrate east of the Appalachians and winter primarily in the Florida wetlands and as far north as the Carolinas (Guillaumet et al. 2012). Favorable wetlands-rich habitats in Florida and the Mississippi alluvial valley and the Appalachian Mountains may influence this divide (Guillaumet et al. 2012). However, cormorants display a great deal of individual variation in migratory routes, with individuals using different migratory routes for spring and fall in the same year (Dolbeer 1991, Guillaumet et al. 2012).

The aquaculture regions of the Southeast have also been suggested as a favorable habitat for wintering cormorants. Large numbers of cormorants use aquaculture-producing areas of the southeast during winter (Glahn et al. 2000, Dorr et al. 2012a). However, Scherr et al. (2010) found few satellite-marked cormorants from n. Lake Huron using aquaculture-producing areas.

Several important fall staging areas have been identified from satellite telemetry in w. Lake Erie, the Eastern Basin of Lake Ontario, Lake Champlain, Chesapeake Bay, and Albemarle and Pamlico sounds (Scherr et al. 2010, Dorr et al. 2012d, Guillaumet et al. 2012). These areas are likely important stopover foraging habitats for migrating cormorants. Potential staging areas of cormorants breeding further west in the Great Lakes and Prairie Provinces are not well documented.

On the Pacific Coast, migrants are evident in British Columbia from late Aug to early Nov; influx into inner coastal waters peaks in early Sep (Campbell et al. 1990b). In coastal Oregon, migrants arrive Jul–Aug; east of the Cascade Mtns., the last migrants depart Oct–Nov (Gilligan et al. 1994). Depart from the Farallon Is., CA, after last young fledge in late Sep (Ainley and Boekelheide 1990). Cormorants marked with satellite tags from a colony at the mouth of the Columbia River, OR, dispersed from the Columbia River estuary 1 Jul to 1 Dec (mean Aug 27th). All tagged cormorants had left the region by mid-Dec, with the exception of a small number of resident birds; post-breeding cormorants dispersed up to 1,805 km from the mouth of the Columbia River estuary; more than half of satellite-marked cormorants wintered north as well as south of the colony (Courtot et al. 2012). Both satellite tags and banding data indicate that cormorants on the Pacific Coast infrequently travel east of the Cascade-Sierra Nevada Range (Clark et al. 2006, Adkins and Roby 2010, Courtot et al. 2012).

Migratory Behavior

Most inland records of migratory flights are of small flocks, <50–100. Along coasts, near-shore flocks may be large (in the thousands). Over water, migrants usually fly low, in wavering lines or irregular V-formations; over land, fly as high as 1,000 m.

An autumn departure from Presqu'Ile Bay, Lake Ontario, was described as follows: “At mid-morning a flock of approximately a thousand cormorants began to take flight from a large protected bay and spiraled upward to a height of several hundred feet. They circled and then flew off to the south, as if to fly across the lake. Several minutes later, however, they returned, resumed their high altitude circling (much the way passerines do during migration before crossing a large body of water) then departed a second time to the south and did not return” (R. D. McRae pers. comm.).

Little information available on daily duration; flights start soon after dawn and continue all day (Nisbet and Baird 1959). Some autumn departures observed as late as 10:00 for overland flights from Boston, MA, toward Narragansett Bay, RI (JJH). Spring departures observed at first light from overnight roosts on Lake Ontario (DVW). No published observations of cormorants migrating by night as well as by day, but flocks have been observed flying in late evening and few have been seen to stop and settle (Nisbet and Baird 1959).

Control and Physiology of Migration

Largest numbers seen in cool, clear weather after passage of cold fronts (Nisbet and Baird 1959). No other data.

Habitat

Occupies diverse aquatic habitats in all seasons; nonbreeding birds are distributed more widely. Most inland breeders winter in coastal areas; increasing numbers winter inland near aquaculture sites (Glahn et al. 2000, King et al. 2010, Dorr et al. 2012a). In all seasons, requires, in addition to feeding habitats, suitable places for daytime resting or loafing and nighttime roosts. Between bouts of fishing, cormorants spend much time perching on exposed sites such as rocks or sandbars, pilings, ship wrecks, high-tension wires, or trees near favored fishing sites. Such daytime resting places (loafing areas) may also be nighttime roosts for some individuals, but roosts are often more remote and used by larger numbers.

Most individuals forage in shallow water (< 10 m deep), typically < 30 km from the colony or roost and within 2.5 km of shore, within sight of land; rarely seen offshore (Stapanian et al. 2002, Dorr et al. 2004, King et al. 1995, Custer and Bunck 1992, Coleman et al. 2005, Dorr et al. 2012a). Numbers increase rapidly wherever prey is readily accessible, and predictable seasonal patterns may result (Dorr et al. 2012a). Proximity of preferred roosts and nesting colonies (which may be limited in number) to foraging areas greatly influences daily flight distances. Some birds nesting (or roosting) on coastal islands fly inland to feed at freshwater sites (JJH).

Habitat in Breeding Range

Occurs on ponds, lakes, artificial impoundments, slow-moving rivers, lagoons, estuaries, and open coastlines. Individuals forage up to 62 km from colony or roost (see Demography and Populations: range, below). Colonies are established at sites safe from ground predators and close to feeding areas (typically < 10 km away; See Wires and Cuthbert 2010); generally these sites have been used as roosts and/or loafing areas for several years. Larger colonies tend to have been occupied longer and on larger island sites (> 1.0 ha; see Wires and Cuthbert 2010). Selects small rocky or sandy islands, where available, and may use artificial sites such as bridges, shipwrecks, abandoned docks, or nesting-towers (Meier 1981). Also nests on mats of emergent vegetation in marshes (Gilligan et al. 1994). When nesting (or roosting) in trees, these trees are usually standing in or near water, on islands, in swamps, or at tree-lined lakes. Ground-nesting may be both the ancestral and the preferred habit for this species, nesting in trees being a response to predators (Lewis 1929). May shift from tree- to ground-nesting at a colony site as trees die and colony grows, but where predators are present, depends for nesting on flooded snags or live riparian trees.

Before and after the breeding season, likely to occur farther from colony sites and to feed and roost in new areas. Seasonal patterns illustrated for Penobscot Bay, ME, where cormorants shifted between river and bay (Blackwell and Krohn 1997). Spring arrivals (Apr) fed largely in fresh water, concentrating at river dams and roosting nearby. In May, they consumed many salmon smolts; in Jun, nestlings on islands in the bay were fed marine fish (see Food habits: diet, below).

Habitat in the Winter Range

Largest numbers occur along southern coasts, where habitat use is poorly known, but, as in breeding habitat, birds require feeding, loafing, and roosting sites. May assemble in tens of thousands on sandbars in coastal inlets. Many cormorants wintering near catfish (Ictalurus sp.) farms in the southeast roost in isolated cypress swamps (Glahn et al. 1996, King 1996, Dorr et al. 2004, King et al. 1995, Dorr et al. 2012a. In Mississippi, morning flights from such roosts to first foraging areas average 15.7 km (range 4-62, n = 33; King et al. 1995a). Birds that roosted in the western delta region of Mississippi moved between 22 and 26 km their next-day location (Tobin et al. 2002). This difference may be affected by geographic segregation based on prey base (Glahn et al. 1995, Dorr et al. in press; see below). Birds subject to harassment to limit foraging on catfish aquaculture moved further to their next day foraging locations (31 km vs 22 km, respectively; See Tobin et al. 2002). In Alabama, radio-marked cormorants moved on average 7.9 km (n = 24; see Dorr et al. 2004) from their night roost to next day locations. The maximum distance moved in one day was 113 km (Dorr et al. 2004).

Sex differences in range and habitat use have been described. King et al. King et al. 1987) found 27 females among 29 cormorants collected in the Houston Ship Channel. For birds wintering inland, males predominated in samples shot at roosts in Mississippi; in catfish production areas, the proportion of males was 0.78 (n = 284), and near the Mississippi River, 0.66 (n = 177; Glahn et al. 1995); in Alabama, 0.48 (n = 77; Glahn et al. 1997). Dorr et al. (in press) found males and females used different geographic areas of the south based on available prey base, including aquaculture. In Mississippi, the median distance from night roost to subsequent day location was 26.3 km for females and 22.1 km for males (Tobin et al. 2002). However, there was no difference in distance moved between radio-marked males and females in Alabama (Dorr et al. 2004).

Historical Changes to the Distribution

From Hatch 1995a, unless otherwise noted. Present as breeders in New England in the 17th century; also at Lake of the Woods, Ontario, in the 18th century (Peck and James 1983). Early records (pre-1900) suggest cormorants were present throughout much of their current range although determination of historical abundance is problematic (Wires and Cuthbert 2006). Numbers and range greatly reduced by the early 20th century, probably from widespread direct persecution and some loss of inland habitat from agricultural clearances (see Conservation and Management, below). Extirpated from New England, Vancouver I., and the w. Aleutians, and probably withdrew from many areas. Subsequent great increases (and decreases) in numbers reflect several human-induced changes (see Demography and Populations, below) and have been mostly within the historical range, except possibly for the Great Lakes, where nesting was first recorded in Lake Superior in 1913, with subsequent eastward spread to the remaining 4 lakes (Weseloh et al. 1995b). This expansion could have represented recolonization of areas from which breeding birds were extirpated before the earliest records (Wires and Cuthbert 2006).

For British Columbia, first breeding record was in the early 1920s, but archaeological evidence suggests this was a return and not a range extension. Expansion into many previously unoccupied arid areas has been enabled by construction of dams—e.g., into e. Colorado, where the species first nested in 1931 (Andrews and Righter 1992); Wyoming, where first nested in 1928 and 73% were nesting on reservoirs in 1986 (Findholt 1988); and S. Carolina (Post 1988c).

Returned to Massachusetts by 1940, and since 1970 has extended its breeding range along the coast to New York City and locally south to merge with the population that is resident in Florida and the Carolinas. Mid-Atlantic states are now (1997) a region of local expansion; first nestings in Virginia in 1978, Maryland in 1990, Pennsylvania in 1996 (Blem et al. 1980, Mcconaughy 1996, Robbins 1996a).

From Prince Edward I., first record of nesting was 1941, but no information about possible earlier occurrences. On Lake Champlain (Vermont/New York), first recorded nesting in 1982; origins of these birds unknown. In Alaska, extended range north to Nunivak I. by 1991 (Tobish and Isleib 1992a), but has not recolonized the w. Aleutians.

In the South, breeding cormorants have returned to many areas although possibly not to their historical extent (Jackson and Jackson 1995), but many winter and nesting reports in the southeastern states (James and Neal 1986, Post and Seals 1991) (Reinhold et al. 1999, Wires and Cuthbert 2006). In Texas, interesting history; returned as a breeder in 1970, after a lapse of 30-40 yr (http://txtbba.tamu.edu/species-accounts/double-crested-cormorant/ ).

Nesting in Yucatán (Mexico) or nearby not reported by Palmer (Palmer 1962a), but was possibly overlooked because this species is sympatric there with the similar Neotropic Cormorant which has been expanding its range northward near breeding Double-crested Cormorants (Hanson et al. 2010). The occurrence of early-winter stragglers, increasingly seen on CBCs throughout much of the interior, may represent a shift in wintering range for the Double-crested. King et al.'s (2010) analysis of banding data suggests the expansion of catfish aquaculture in the southeast may have influenced cormorant migration and wintering behavior; substantial numbers occur near aquacultural ventures in Mississippi and other southern states (Glahn et al. 2000, Sauer et al. 2006).

Expanded rapidly in Maryland (lower Chesapeake Bay), 1991-2006: 1246 to 1890 breeding pairs, and 1 to 14 colony sites (Brinker 2010).

Fossil History

Cormorants are quite numerous in the fossil record, extending back to the Oligocene. The present species is represented by Pleistocene and prehistoric records, notably from coastal sites, widely distributed within the present breeding range (Brodkorb 1963a, Hatch 1995a). The only long archaeological record is from Amchitka I. in the Aleutians (from 2,650 yr; Siegel-Causey et al. 1991).

Recommended Citation

Dorr, Brian S., Jeremy J. Hatch and D. V. Weseloh. 2014. Double-crested Cormorant (Phalacrocorax auritus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA. https://doi.org/10.2173/bna.441