Large, dark cormorant. Typical length 70 to 90cm, body mass 1.2 to 2.5 kg. Sexes are alike. Males are slightly larger than females. Adults have black or dark-brown plumage, with a dull greenish or bronze gloss. The orange-yellow skin of face and throat is distinctive throughout the year. The "double crest" feathers are variable and are fully developed for only a short time early in the year. This is the only seasonal change. Has totipalmate feet in which all 4 toes are connected by web (Hatch and Weseloh 1999).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see Marks et al. 2016, Birds of Montana.
Western Hemisphere Range
Birds breeding east of the Rocky Mountains generally winter along the Gulf of Mexico from Florida to Texas (Dolbeer 1991). In the Bozeman area they are seen during spring migration from April 10 to May 30 and intermittently from July to October 10, with a peak in the fall around September 6.
Occupies diverse aquatic habitats in all seasons. Requires, in addition to feeding habitats, suitable places for daytime resting or loafing and nighttime roosts (Hatch and Weseloh 1999).
At most sites eats almost entirely fish preferring slow-moving or schooling species. (Hatch and Weseloh 1999).
Typically a single brood. Second broods per season are rare. Clutch size is 1 to 7 eggs with 4 being normal. Nesting is done in colonies (Hatch and Weseloh 1999). Nesting occurs in late May to early June.