Size 30-36" (76-91 cm). Idaho's only breeding cormorant. A goose-sized, black or dark bird. Immature birds light brownish. Breeding adults have inconspicuous tufts on either side of the crown of the head. Head normally uplifted. Distinguished from other cormorants by its orange-yellow throat patch. Cormorants will fly in lines or wedges, similar to geese, but are silent. Neck kinked when in flight.
Similar Species- No other cormorants normally breed in Idaho. Very distinct.
Breeds throughout much of North America (locally in interior), from southern Alaska, Manitoba, and Newfoundland, south to Gulf Coast and northwestern Mexico. Winters throughout most of coastal breeding range.
Feeds primarily on nongame fish.
Dives from water surface to obtain food; usually feeds in water less than 15 m deep. Forages cooperatively. Nests mostly in colonies; entire colony will nest either in tree or on ground. Increased sea surface temperatrues, such as those associated with El Nino events, were correlated with decreases in nesting populations in Washington. Species is common transient and summer breeder in Idaho, where nesting areas are easily disturbed by man. Gulls prey on eggs. Young can suffer from heat prostration.
Both sexes in turn incubate 2-9 eggs (usually 3-4), for 24-25 days (southeastern Idaho study found average of 3.5 young for 12 nests). Young first fly to water at about 35-42 days, and become independent at 10 wk. Adults usually breed by third year.
|Status:||Protected nongame species|
Trost, C.H. and A. Gerstell. 1994. Status and distribution of colonial nesting waterbirds in southern Idaho, 1993. Dept. Biol. Sciences, Idaho St. Univ., Pocatello. 101pp.