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Double-crested Cormorant

Phalacrocorax auritus

Order:
Suliformes
Family:
Phalacrocoracidae
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Adult breeding (Alternate) Double-crested Cormorant; Saskatoon, SK; May.

Adults have black or dark-brown plumage, with a dull greenish or bronze gloss that may be absent from worn feathers. The orange-yellow skin of face and throat (gular region) is distinctive throughout year. The “double crest” is a poor field mark; these feathers are variable and are fully developed for only a short time early in year. P. a. auritus breeds over most of range in e. and central North America; largely migratory, wintering from mid-Atlantic Coast to Gulf of Mexico. Crest, when present, is black and curled. Taken 4 May, 2013, in Saskatoon, Saskatchewan, Canada. The following is a link to this contributor's image via Birdshare: Kirchmeier.

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Adult breeding (Alternate) Double-crested Cormorant; Downey, Los Angeles Co., CA; March.

P. a. albociliatus breeds along the Pacific Coast from British Columbia to Baja California and Sinaloa, and inland, possibly as far east as New Mexico, Utah, and Montana. Crest variably mixed white and black. Note bright turquoise eyes and mouth lining in adult breeding condition. Taken 9 March, 2012 in Downey, California. The following is a link to this contributor's image via Birdshare: Maureen Sullivan.

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Juvenile and adult Double-crested Cormorants in nesting tree; Moonglow Dairy, CA; June.

Taken 30 June, 2013, at Moonglow Dairy, California by Brian Sullivan.

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Adult breeding (Alternate) Double-crested Cormorant; Orlando, Orange Co., FL; March.

P. a. floridanus is resident in Florida and Caribbean. Taken 14, March 2014, at Orlando, Florida. The following is a link to this contributor's image via Birdshare: Steven Bach.

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Second-winter Double-crested Cormorant; Moss Landing, CA; October.

Second-winter Double-crested Cormorant with wings open. Spread wing posture may facilitate drying of plumage; cormorants are thought to have wettable plumage that facilitates underwater pursuit of prey. Taken 9 October, 2010 at Moss Landing, California by Brian Sullivan.

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First-summer Double-crested Cormorant; Elkhorn Slough, Monterey Co., CA; August.

Taken 31 August, 2007 at the Elkhorn Slough, California, by Brian Sullivan.

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Adult Double-crested Cormorants with juveniles at nest; Almond Marsh, Lake Co., IL; June.

Taken 23 June, 2012, at Almond Marsh, Lake County Forest Preserve District, Lake County, Illinois. The following is a link to this contributor's image via Birdshare: JanetandPhil.

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Figure 7. Annual cycle, Ontario.

Annual cycle of breeding, migration, and molt of Double-crested Cormorants from northern populations (Ontario). Thick lines show peak activity; thin lines, off-peak.

Large, dark cormorant; typical length 70–90 cm, body mass 1.2–2.5 kg; sexes alike. Males slightly larger than females, but regional (subspecific) differences are much greater (see Measurements, below). Adults have black or dark-brown plumage, with a dull greenish or bronze gloss that may be absent from worn feathers. The orange-yellow skin of the face and throat (gular region) is distinctive throughout the year.

The “double crest” is a poor field mark; these feathers are variable and are fully developed for only a short time early in year. This is the only seasonal change. Immatures are duller and variable, usually paler on upper breast and darker on belly, occasionally uniformly pale below.

Similar Species

Occurs with all other North American cormorants in appropriate coastal areas, but is the only cormorant in most of the interior. Great Cormorant, which breeds in e. Canada and Maine and winters along the Atlantic Coast of the U.S., is similar but somewhat larger. In adult Great Cormorants, yellow facial skin is bounded posteriorly by a distinct white feathered patch, and in full Definitive Alternate (breeding) plumage there is a large patch of white feathers on each thigh, and white plumes over much of the head. Immatures of the 2 species are similar, but young Double-cresteds have a pale breast and throat with darker belly, while young Greats show the reverse pattern.

In the southwestern and southeastern US, Mexico, and the Caribbean (especially during postbreeding dispersal), Double-crested can be confused with Neotropic Cormorant (Phalacrocorax brasilianus), which is reported as an occasional vagrant north to Minnesota (Hanson et al. 2010). The latter species is smaller and more slender, and has a longer tail and throat-pouch that differs in color and shape; the gular pouch of the Neotropic forms a horizontal V, colored pale yellowish brown and bordered by a narrow band of white feathers ending in a point behind and below the eye. In the Double-crested Cormorant, the pouch is larger, rounded, and more brightly colored. Separation of immatures is more difficult; gular pouches are duller at this age, but the color of the supraloral skin (between eyes and bill) is brighter in the Double-crested and darker in the Neotropic (Telfair II and Morrison 1995). Immature Neotropics are more uniform in color than are bicolored young Double-cresteds (see Appendix 3  for measurements).

Other cormorants found in w. North America, with the exception of the similar Neotropic (see above), are strictly coastal in distribution. Compared to the Double-crested Cormorant, the Red-faced (P. urile) and Pelagic (P. pelagicus) cormorants are noticeably small and slender, with red facial skin and gular pouch; breeders have white flank-patches, and immatures are uniformly dark. Brandt's Cormorant (P. penicillatus) is similar in size and shape to the Double-crested, but its gular pouch is less conspicuous and colored blue or violet, with a band of short, buff feathers posterior to it. Immatures are generally darker than young Double-cresteds, with uniform rather than bicolored underparts.

Detailed Description

Double-crested Cormorants have 10 functional primaries, 19–20 secondaries (including 3–4 tertials), and 12 rectrices; cormorants are diastataxic (see Bostwick and Brady 2002) indicating that a secondary has been lost evolutionarily between what we now term s4 and s5. Geographic variation in appearance slight to moderate (see Systematics: Geographic Variation); the following molt and plumage descriptions pertain to the species as a whole, except where briefly noted.

Plumages

Following based on plumage descriptions in R. Arbib (in Palmer 1962a), Oberholser (Oberholser 1974c), Johnsgard (Johnsgard 1993), and Nelson (2005); see Pyle (2008) for specific age-related criteria. Sexes show similar appearances in all plumages; male average larger (see Measurements). Definitive Plumages typically assumed at Third or Fourth Basic and Alternate Plumages.

Natal Down

Present primarily Apr–Jul, on or near natal territory. Hatchlings naked, except for a very few filaments, chiefly on rump and lower wings (Mendall 1936a). By 2 wk short black down covers body; head and neck less-densely covered. Two sets of down described for other cormorants but growing from different groups of follicles, so best considered one coat of down.

Juvenile (First Basic) Plumage

Present primarily Jun–Mar. Head mostly dark brownish gray to pale brown, shading to grayish white on chin; throat whitish with brown mottling. Upperparts and upperwing coverts dark grayish brown with darker feather margins, providing scaly appearance, darkest on lower back and rump; feathers shorter and more pointed than in later plumages and lacking gloss (Pyle 2008). Remiges and rectrices dark brown, uniform in quality, averaging narrower and more tapered at tip than basic feathers. Remainder of underparts mottled brown and whitish.

Formative Plumage

"First Basic" or "Basic I" plumage of Humphrey and Parkes (1959) and later authors; see revision by Howell et al. (2003). Present primarily Dec-Jun. Similar to Juvenile Plumage but juvenile feathers of head, neck, and breast become increasingly bleached through winter and spring, to pale brown or whitish, variably mixed with scattered fresher, darker brown, glossier, and more-rounded formative feathers. Ornamental crest plumes not developed or rudimentary at best. Juvenile upperwing coverts, primaries, and rectrices retained, increasingly worn and bleaching to paler brown

Second Basic Plumage

Present primarily Jul–Jun. Similar to Definitive Basic Plumage but feathering dark brown with less gloss; head, neck and breast washed brown or variably mixed with brown and glossier black feathers; feathers semi-rounded, intermediate between juvenile and definitive feathers in shape, fringed with darker blackish (Pyle 2008). During molt in Jul–Jan, outer primaries, older medial secondaries, and older rectrices retained juvenile, markedly browner and narrower than incoming basic feathers. Following completion of molt, 1–4 juvenile outer primaries (among p7–p10) and corresponding primary coverts and 1–6 juvenile secondaries (among s3–s4 and s8–s11) often retained, brownish, bleached and abraded by second summer. Some individuals undergo a complete Second Prebasic Molt and show remiges and rectrices more-similar to those in Definitive Basic Plumage though earlier-replaced feathers (including inner primaries and rectrices) often washed browner, when fresh, than in later plumages.

Second Alternate Plumage

Present primarily May–Jul. Similar to Second Basic Plumage but a few to some feathers of head and neck usually replaced, glossier black, fully rounded as in definitive feathers. Retained basic feathers become more bleached, paler brown, sometimes approaching whitish color of first-cycle Formative Plumage. Ornamental crest feathers present but can average less extensive than in Definitive Alternate Plumage. Age-determination as in Second Basic Plumage, by medium-dark brown body feathers and retained juvenile wing feathers.

Definitive Basic Plumage

Present primarily Aug–Jul. Head, neck, lower back, rump, and uppertail coverts black with dull greenish gloss; feathers of upper back, scapulars, and upperwing coverts brownish gray with bronze gloss present to varying degrees, widely margined with glossy black, forming scaled appearance to upperparts when fresh. Feathers broader and rounder than in previous plumages (Pyle 2008). Tail graduated (wedge-shaped), black to blackish brown; alula black; remiges and rectrices black to brownish black (browner when worn), with dull gloss on dorsal surface. Short, thick, light-brownish down present but invisible below feather coat. No aftershafts. Some individuals in Third Basic Plumage may show slight brownish wash on breast and retained juvenile feathers (among p10 and s9–s11) among two generations of basic feathers (Pyle 2008), but most indistinguishable from later basic plumages.

Definitive Basic Plumage often characterized by 2-4 sets of basic feathers among primaries and secondaries, in Staffelmauser patterns; replacement sets in primaries defined by a worn feather immediately distal to a fresh proximal feather, and those of secondaries showing mixed generations in various sequences (Pyle 2006, 2008). Older basic feathers not as contrastingly narrow and brown as retained juvenile feathers after incomplete Second Prebasic Molt. Number of sets in primaries equates to minimum ages of 2–5 years (Pyle 2008); individuals of northern breeding populations may average more sets than those of southern populations.

Definitive Alternate Plumage

Present primarily Mar–Aug. Similar to Definitive Basic Plumage except some feathers of head, neck, and often breast replaced with glossier feathers. Ornamental. ear-like nuptial crests, source of the specific name auritus, located above and behind eye in spring. The crests are modified contour feathers, narrow, with separated barbs; color variable—black in east, mostly white in west; length to 78 mm in western birds, to 38 mm in east; plumes straighter in east, curlier in west. Up to 88 plumes recorded but usually 40–60 per side in male, fewer in female. Plumes occasionally also present on upper neck, and some individuals have long white filoplumes on head, neck, and thighs; variable and often visible only in the hand (much less conspicuous than in some other cormorant species). Retained basic feathering loses sheen and becomes progressively browner.

Molts

General

Molt and plumage terminology follows Humphrey and Parkes (1959) as modified by Howell et al. (2003, 2004). Double-crested Cormorant appears to exhibit a Simple Alternate Strategy (cf. Howell et al. 2003, Howell 2010), including incomplete-to-complete prebasic molts, a limited-to-partial (occasionally absent) inserted molt within the first cycle, and limited prealternate molts in definitive cycles (R. Arbib in Palmer 1962a, Oberholser 1974c, Cummings 1987, Howell and Webb 1995, Nelson 2005, Pyle 2008; Figure 7). The single inserted first-cycle molt appears to be homologous with a preformative molt (Pyle 2008) but may also include a first prealternate molt, or represent a merging of these two molts from those of ancestral taxa. No geographic or sex-specific variation in molt strategies reported, although variation likely exists as related to migratory strategies; e.g., northern-breeding North American subspecies P. a. auritus and cincinatus are more migratory than other populations and might show adaptive shifts in molting patterns, such as slower and less-extensive replacement of feathers per year (Pyle 2008). Extent of molt also likely varies considerably with variable inter-annual food-resource availability (see Breeding), which may mask geographic differences in timing and extent.

Prejuvenile (First Prebasic) Molt

Complete, primarily Jun–Aug, in the nest. Contour feathers reportedly grow from different sets of follicles than down feathers. Primary sheaths visible by 13–14 d and erupt by 16–19 d, when sheaths of uppertail coverts and feathers of sides and back have appeared. By 21–23 d remiges 2.5 cm long; development then slows, and by 28 d remiges are 6 cm long. At 35 d, feathers on back, breast, lower underparts, and forelimbs are well grown, but none on head and neck. By 42 d, few feathers on head, greenish gloss of dorsal feathers evident; neck still thickly down-covered. Neck feathers last to complete, by 49–58 d, but few data.

Preformative Molt

"First Prebasic" or "Prebasic I" Molt of Humphrey and Parkes (1959) and some later authors; see revision by Howell et al. (2003). Absent to partial, primarily Nov–Apr (Figure 7), on non-breeding grounds. Includes no to most feathers of head, neck, and back but no wing or tail feathers. Timing of last-replaced feathers during Preformative Molt may overlap that of first-replaced feathers (inner primaries and tertials) during Second Prebasic Molt. This molt presumed to have evolved from an ancestral Preformative Molt but may also include a First Prealternate Molt (see above), if individual feathers are replaced twice within this period.

Second Prebasic Molt

Incomplete to Complete, Feb–Dec, occurring primarily on non-breeding grounds. Similar in sequence to Definitive Prebasic Molt but occurs earlier in year due to lack of constraints related to breeding, and for migration for individuals remaining on winter grounds for first summer. Includes most or all body feathers, wing coverts, and rectrices, but usually not all primaries and secondaries. As in other cormorants studied (Potts 1971; Rasmussen 1987, 1988; Telfair II and Morrison 1995; Filardi and Rohwer 2001), remiges exhibit Staffelmauser (stepwise) sequence and pattern of flight-feather replacement (Stresemann and Stresemann 1966; Pyle 2006, 2008; see Definitive Prebasic Molt). During Second Prebasic Molt the outer 1–4 juvenile primaries (among p7–p10) and corresponding primary coverts and 1–6 juvenile secondaries (among s3–s4 and s8–s11) often retained to commence Staffelmauser. Second Prebasic Molt can also be complete in some individuals, especially among populations breeding in southern portions of North American range.

Second And Definitive Prealternate Molts

Limited to Partial, Jan–Apr (Figure 7), often commencing on non-breeding grounds and completing on breeding grounds. Includes no to a few feathers of the head, neck, back, and breast. Traditionally considered to include ornamental nuptial crests (see Definitive Alternate Plumage), but these feathers are lost by Jun, and may represent specialized filoplumes as also occur on upper neck and sometimes head and thighs. These ornamental plumes may thus not represent alternate feathers (Pyle 2008); study needed.

Third And Definitive Prebasic Molts

Complete, primarily Apr–Jan (Figure 7medialink), occurring primarily on non-breeding grounds. Most body feather molt occurs in Jul-Nov; molting of remiges occurs primarily in Jul-Nov but can extend into winter and possible spring in some cases, after slowing or suspension for winter. Third Prebasic Molt likely commences earlier than later Definitive Prebasic Molts, on average. Primaries replaced distally (p1 to p10), and secondaries replaced proximally from s1 and s5 and distally from the tertials. Sequence of rectrix replacement less clear but may generally be replaced distally (r1 to r6) on each side of tail, with some variation possible. One adult reportedly replaced rectrices twice during one cycle of remigial replacement (Cummings 1987). In P. pelagicus

mean primary growth rate estimated at 4.6 mm per day, an average of 2.9 primaries may be growing simultaneously, and average time to complete prebasic molts estimated at 21-36 weeks (Filardi and Rohwer 2001); growth rates likely similar or slightly slower in Double-crested Cormorant.

Molt pattern among primaries and secondaries exhibits Staffelmauser (Stresemann and Stresemann 1966; Filardi and Rohwer 2001; Pyle 2006, 2008) whereby incomplete molts result in series of commencement points within primaries and secondaries, beginning with termination points of previous prebasic molt and also initiating new series commencing at p1, s1, s5, and/or the tertials. By third of fourth year, replacement typically proceeds in 2–4 waves through the wing, resulting in 2–4 "sets" (generations) of feathers following completion of molt. Staffelmauser appears to be a product of insufficient time to undergo a complete wing-feather molt but has adaptive benefits in producing multiple small gaps in the wing during molt, which retains wing integrity and ability to fly and forage (Tucker 1991, Shugart and Rohwer 1996, Pyle 2005).

Bare Parts

Following descriptions based on R. Arbib (in Palmer 1962a) and Johnsgard (Johnsgard 1993). Regional and seasonal variation and age changes not adequately known, requiring careful study of live birds.

Bill And Gape

In juveniles, upper mandible dark brown, becoming yellowish ventrally; lower mandible paler. In adult, upper mandible black, mottled with grayish or dull yellow along sides sometimes appearing scaly; lower mandible yellowish to pale bluish, mottled dusky. Mouth of nestling and juvenile pink; of nonbreeding adult, variable, flesh to yellow or pale blue. Mouth of (pre)breeding adult, bright cobalt blue to dull blue with greenish reflections; this color lost after breeding.

Iris

Iris black when eyes open, brownish in juvenile, bright blue-green or turquoise with narrow silvery-green circle around pupil in breeding adult. Transitions with age and/or season not reported. Orbital ring variable, not well characterized; some are dull yellow, others gray-blue marked with white (JJH). Eyelid colors of adults reported to differ geographically or individually, from bright blue (generally), or light blue spotted with white (in floridanus) to yellow or orange (Johnsgard 1993).

Bare Skin On Head And Neck

At hatching skin on head and neck mostly pink, with faint lavender and scattered black markings; yellowish by 2 wk. In juvenile, bare lores variably whitish, yellowish, or dusky. Gular skin dull yellow, with black marking. In prebreeding adult, bare skin of face and pouch generally orange, seasonal variation not well known; supraloral region (above and anterior to eye) bright orange, central loral area darker and dotted with black. The feathered posterior boundary of the orange pouch runs directly across the throat, resembling Neotropic Cormorant but different from Great and Brandt's in which throat feathers extend forward forming an inverted V. After breeding, facial and gular skin is duller and more yellow. Central loral area has inconspicuous vestigial feathers, with bare skin above and below.

Legs And Feet

Dark brown at hatching; soon darken to dull black, unchanged thereafter. Tarsi thick, laterally flattened, and relatively short.

Measurements

Substantial regional variation. Most reports are based on small samples that were not measured by same person. In each area males average about 2–6% larger than females (12–15% by mass ), but there is considerable overlap. Size (of breeders) decreases from west to east and from north to south. These differences, and accompanying crest characters, have not been examined comprehensively.

Linear Measurements

For all specimens combined (see Appendix 3 ), ranges of measurements are large: culmen, 43–63 mm; wing, 259–349 mm; tarsus, 49–74 mm. Tail is of doubtful value because it is often extensively worn. A discriminant function, using wing chord and rectrix width, correctly sexed 94% of an unsorted sample of 507 breeding birds from Quebec (Bédard et al. 1995b). For wintering birds in Mississippi, Glahn and McCoy (Glahn and McCoy 1995) concluded that wing chord, culmen depth, and culmen length were the most useful variables for identifying sex; mean culmen depth differed by 11%: male, 17.6 mm ± 0.1 SE (range 15.5–20, n = 160); female, 15.8 mm ± 0.2 SE (range 14–18, n = 40). This feature has rarely been reported, but might be a visible character that is useful in some field situations (see Koffijberg and Eerden 1995 for Great Cormorant).

Mass

Regional differences are large and no data are available from the West coast and Alaska, where the largest birds occur. Mean mass of small southeastern birds is scarcely half that of northern and western birds and the extremes span almost a threefold range (1 to 3 kg).

All samples that follow were collected in the breeding season, with the exception of those from Mississippi:

From New Mexico (Watson et al. 1991): male, mean 2,453 g (range 2,200–2,750, n = 15); female 2,056 g (range 1,750–2,400, n = 17).

From Quebec (Bédard et al. 1995b): male 2,089 ± 5.32 SE (n = 763); female 1,831 ± 7.17 SE (n = 375).

From Florida (Owre 1967a): male 1,758 (range 1,327–2079, n = 6): female 1,535 (range 1,391–1,665, n = 5).

From the Bahamas (Watson et al. 1991): male 1,270 (n = 1); female 1,112 (range 1,036–1,175, n = 3).

From Mississippi (in winter, Glahn and McCoy 1995): male 2,498 ± 16 SD (range 2,000–3,000, n = 160); female 2,162 ± 29.8 SD (range 1,650–2,600, n = 41).

For additional data, see Marshall and Erickson 1945 (Minnesota), Kury 1968 (Maine), Hartman 1961 (Florida).

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