Courtship behavior by Double-crested Cormorants (Nannopterum auritum) in the city? That’s what Mr. WordsandBirds noticed when he and I birded near the University of Washington in Seattle last week. We’d never seen this behavior in DCCOs before. That’s because, while these snaky, fish-eating relatives of frigatebirds and boobies are common winter residents of our inland waters, they typically migrate to breeding colonies on the Pacific Coast in April (like now). That’s about 135 miles west.
Birds of the World says point-blank, “Pair Bond: Evident only at nest.” Further, males arrive first, unpaired. However, the birds we saw seem to have other plans. Here’s a look at the behavior we observed:
By this point they were beginning to attract onlookers among their peers:
I discovered a reference in Birding in Seattle and King County, by Gene Hunn indicating that Double-crested Cormorants have bred in King County, but only rarely. This behavior didn’t appear rare, however, as the pair next to the one we’d watched shows:
All About Birds says a male cormorant will migrate to a breeding colony, choose a nest site and then, to attract a female, “stand with his breast down and bill and tail up, showing off the crests on his head and bright colors of his neck and his eyes, grunting and slightly waving his outstretched wings. When a female arrives, she is greeted by the male opening his mouth into a gape, showing off the blue inside.”
We never saw such a display, nor whether either male had a blue mouth. Such courtship behavior may have preceded our visit, meaning that these two pairs are more advanced in their pair bonding. DCCOs breed on average by age 3, but most not until the beginning of their fourth year. So one hypothesis is that these birds are subadults, who are playing house like children, or going steady like teens. I emailed several experts for this diary but haven’t yet received a reply. It’s a mystery that bears watching.
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Btw, Double-crested Cormorants historically have suffered from persecution (being shot at) and pesticides (from eating contaminated fish). Between 1966 and 2019, however, their populations increased by 2.6 percent per year, and they’re now a species of low conservation concern.
Conflicts with fisheries in the 2000s resulted in management orders from the U.S. Fish and Wildlife Service, including egg-oiling and culling. A more recent conflict is at the Columbia River. About 30,000 birds, then the largest colony of Double-crested Cormorants in North America, were roosting on an island, chowing down on endangered salmon — about 20 million of them — prompting the Army Corps of Engineers to kill the birds to save the salmon. A group of DCCOs escaped to the Astoria-Megler Bridge, where salmon are now about their only food source. The full story is complicated, and explained in detail here:
Fixing the Columbia River cormorant disaster: ‘How could this have come out any worse?’ | Tri-City Herald
Sources: All About Birds; Birdweb; Birding in Seattle and King County, by Gene Hunn; Lives of North American Birds, by Kenn Kaufman; and Birds of the World (subscription).
Does anyone have insight into the mystery of the courting cormorants? Have you seen their courtship behavior? If not, what’s up in nature near you? Let the comments begin.
In gratitude: