“
Hey, Hey Baby I Wanna Know If You’ll Be My Girl…” No offense to Alabama, Ringo, Conway Twitty or the myriad others who have covered this song, but double crested cormorants have been “airing” their version for thousands of years. June and July are the peak months of the mating season for these gregarious birds.
Double crested cormorants breed in large colonies, either in trees or on the ground. The males arrive at the breeding colony first to choose nest sites. While the communal nesting provides males with lots of buddies, it also means more competition for a girlfriend. It’s tough to stand out in a crowd when your rival is a wing’s length away.
The first step in luring a mate is looking good. During winter, the mostly black cormorants sport a smooth head, long neck, and a muted yellow-orange throat patch. Just for the breeding season, double-crested cormorants grow two feather crests on their heads that extend behind the eyes. Their eyelids become blue and the skin on the neck, face, and throat turns bright orange. This “outfit” is much spiffier than the winter duds.
After he finds a suitable nest site, the male starts to advertise for a mate. He hopes to tempt a gal with a wing-waving display. He stands on his chosen nest site with his breast down, tail cocked upward and forward, and bill pointed upward. This posture shows off the brightly-colored skin on his head and neck. He raises and lowers his wing tips a few times in synchrony with head movements that flash his crests, and croons loud ugh-ugh-ugh sounds. When a potential mate is lured in, the male gapes his mouth in a recognition display. He opens his bill to reveal the bright blue lining, stretches his neck and waves his head slowly and calls ah-r-r-r-r-t-t.
If the enticed female responds with a similar recognition display, the two form a monogamous pair. After forming a pair, double-crested cormorants lose their crests. This, like a wedding ring for humans, tells other cormorants that they are no longer available.
The courtship isn’t quite over yet. The male cormorant wants to be sure his mate is pleased with the partnership. He performs an elaborate courtship dance in the water where he presents the female with nest material. He spares no effort to bring her the best “junk” – sticks, twigs, fishnet, deflated balloons, paper cups, and even the occasional dead bird. The female builds the nest and guards it from other colony members who would otherwise steal the precious nest materials.
After nest construction is complete, the female lays up to seven pale bluish-white eggs.
Both male and female birds share incubation and feeding of the chicks. Cormorants have the unusual habit of incubating their eggs by wrapping the webs of their feet around them. The young begin to leave the nest when they are 3 to 4 weeks old. They can fly at about 6 weeks and dive at 6 to 7 weeks. The chicks become completely independent of their parents by 10 weeks of age.
Where to Look:
Cormorants are generally found on lakes and reservoirs in eastern Colorado in the summer. They are very common in urban areas along the Front Range. In the Denver area, try City Park, Chatfield State Park (Site 59), Bear Creek Lake Park (Site 54), Barr Lake State Park (Site 41), and Rocky Mountain Arsenal National Wildlife Refuge (Site 62). In Fort Collins, try the Fort Collins Greenbelt (Site 33). Sites in southeastern Colorado include Limon Wetland (11), and Pueblo Reservoir/Lake Pueblo State Park (84). A few have been documented at higher elevations including some at MacFarlane Reservoir in North Park, Antero Reservoir in South Park (Site 77) and Eastdale Reservoir in the San Luis Valley.