Appearance

Sexes alike at all stages, except male slightly larger (see Measurements, below).

Molts have received little careful attention. They appear to be long-lasting and ill defined. The following is derived from R. Arbib (in Palmer 1962), with additional information (some conflicting) from Howell and Webb 1995, Cummings 1987, and Oberholser 1974 . Also from related species, especially P. brasilianus (Telfair and Morrison 1995) and P. aristotelis (Potts 1971). These accounts lack consistent reference to marked birds of known age and are substantially conjectural. Feathering is not a safe criterion of age; some 2-yr-olds appear younger than some 1-yr-olds. As in other cormorants studied, primaries are replaced from innermost to outermost, and several generations may be present simultaneously because of successive cycles of primary replacement, each starting at P1 and taking >1 yr to complete. During early cycles, the feather generations differ substantially in chronological age, and P10 may be very worn when first replaced, but in adults each primary is probably molted annually. Molting of rectrices has no clear pattern. One adult replaced rectrices twice during one cycle of remigial replacement (Cummings 1987). However, timing and possible sex differences have not been examined. Relationship of molt to migration not known; subspecies P. a. auritus is exceptionally migratory compared to most cormorants and might show adaptive shifts in molting patterns.

Hatchlings

Naked, except for a very few filaments, chiefly on rump and lower wings (Mendall 1936). The body skin is shiny, translucent brown; outlines of viscera visible. (See also Breeding: young birds). Skin turns black within 48 h, and short, black down covers body by about 2 wk; head and neck sparsely covered. Two sets of down described for other cormorants, growing from different groups of follicles.

Juvenal Plumage

Variable; acquired late summer (age 2 mo) and retained until following spring, and part is retained until age of about 13 mo. Head mostly dark brownish gray to pale brown, shading to grayish white on chin; throat whitish, with brown mottling; upperparts dark grayish brown, with darker feather margins, providing scaly appearance, darkest on lower back and rump; underparts mottled brown and whitish; remiges and rectrices dark brown.

Basic I And Alternate I Plumages

Acquired by gradual molting from first winter, through spring and possibly summer. Some feathers probably renewed twice (thus, Alternate), others once; worn Juvenal flight-feathers are diagnostic of these plumages. Great individual variation, inadequately described. Generally darker than Juvenal, head and neck brownish, feathers may have lighter margins. Underparts variably fuscous; occasionally all white.

Basic Ii Plumage

Probably acquired by complete molt in fall and/or winter when >1 yr old. Resemble Basic I, generally darker brown, flight-feathers darker than those remaining from Basic I.

Alternate Ii Plumage

Acquired by late winterspring molt (age <2 yr). New feathering acquired on head, neck, and parts of body; remainder is retained Basic II plumage. Resembles older birds at same stage, but lacks crests, or may have very small crests.

Definitive Basic Plumage

Acquired by complete molt in late summer. Head, neck, lower back, rump, and uppertail-coverts all black, with dull greenish gloss. Feathers of upper back, scapulars, and wing-coverts brownish gray, with bronze gloss present to varying degrees, widely margined with black. Alula black; remiges and rectrices black to brownish black (browner when worn), with dull gloss on dorsal surface. Tail is graduated (wedge-shaped), with 12 rectrices, often very worn. All feathered areas are covered with short, thick, light-brownish down, invisible below feather coat. No aftershafts.

Definitive Alternate Plumage

New feathering on head, neck, and upper back acquired by partial molt in Jan–Mar. Includes the allegedly earlike nuptial crests, source of the specific name auritus . These crests, located above and behind eye, are lost by Jun, before breeding is completed. Not known if they are replaced for remainder of cycle by inconspicuous feathers. 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. Up to 88 recorded, but usually 40–60 per side in male, fewer in female. Occasionally also on upper neck. 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 species of Phalacrocorax). Remainder of feathering is retained Basic plumage, which loses sheen and becomes progressively browner.

Following descriptions based on R. Arbib (in Palmer 1962) and 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; 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 in breeding adult, with narrow silvery-green circle around pupil. 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. By 2 wk, yellowish. 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.