Birder’s Notebook: Pelagic Cormorant
I’ve always enjoyed finding pelagic cormorants perched on the rocks at Cape Nome, their glossy black breeding plumage flashing with green and blue iridescence in the sun. Near Nome it is common to see them flying purposefully along the coast or surfacing and diving for fish in our coastal waters.
This summer, pelagic cormorants caught my attention and interest more than usual. In June, I watched them ferry nesting materials to their cliff-nesting sites on Sledge Island, then engage in lengthy, dramatic and entertaining bathing rituals.
Later in the summer I watched adults feeding their young at Bluff, where cormorants were the only obviously successful breeders on those seabird cliffs. I was inspired to learn more about these sometimes underappreciated birds.
The name “pelagic cormorant” is a bit of a misnomer. Pelagic refers to something “of the open ocean,” but these are coastal birds, seldom seen far from land. When they do venture further from shore they are usually associated with ice or floating debris.
Pelagic cormorants are the smallest of Alaska’s three cormorant species and the only one commonly found in our region, where they are common breeders on coastal cliffs throughout Norton Sound and the Bering Strait.
Cormorants from our region typically winter in the Aleutians and southern Bering Sea. If open leads or polynyas allow, however, some may show up as far north as Saint Lawrence Island waters during the winter.
In this region, the pelagic cormorant’s migration route is relatively short. The birds return to regional waters from late April through May, with peak arrivals in mid-May. Timing depends on snow melt on the cliffs and sea ice breakup near the nesting cliffs.
Pelagic cormorants nest in pairs or small colonies on exposed cliff faces and sea stacks along rocky shorelines. They don’t try to physically defend their nest or young from predators. Instead, they depend on nest inaccessibility for protection.
Males return first to the cliffs to select and claim a nest site, usually on a narrow ledge along the face of a sea cliff. Often the previous year’s nest is reused. If rival males intrude, they are met with aggressive displays and fights with jabbing and billgrasping can erupt.
When the females arrive, males attempt to attract a mate with wingwaving displays and flashes of their white flank patches. If a female lands for a closer look, the male further entices her with vigorous head bobbing and by showing off the bright red lining of his mouth.
Once a pair bond is established, it is a monogamous relationship for the season. Both sexes use an elaborate repertoire of displays and vocalizations to reinforce their pair bond throughout the breeding season.
Male and female work together to build a bulky nest of grasses and other plant materials, feathers and marine debris. The precariously placed nest is cemented to the ledge with excrement. Additional nesting material is added throughout the nesting season.
Egg laying begins in late May and continues through June. An average of three to four eggs is laid, one every two days. Both parents incubate for about 28 days, beginning when the first egg is laid.
Eggs laid first, hatch first. This helps to adjust brood size according to conditions and food availability. If food is plentiful, all chicks may survive. But if food is limited, the smaller, later-to-hatch chicks die quickly. This is a strategy used by many bird species that reduces competition for food and increases chances of survival for the remaining young.
Both parents brood, feed and tend the nestlings. When temperatures are low, the young may be brooded for three weeks or more. When exposed nesting sites become too warm, the parents bring wet vegetation to cool the chicks.
The parents regurgitate food, mostly fish, into the mouths of their young. The chicks fledge in 49 to 60 days, sometimes before they can fly, launching of the cliff and flapping helplessly to the water below. The parents continue to feed and protect their young for up to month on the water after they fledge.
Medium-sized fish make up a large part of the pelagic cormorant’s diet, but they also eat crustaceans, particularly shrimp and other invertebrates.
Pelagic cormorants are expert fishers, diving for over two minutes, up to depths of 138 feet to seize prey with their hooked bills. Using their big feet to swim and steer underwater, they pursue schools of fish, often striking from below. They also seek out fish hiding in the rocks and pry invertebrates off rocks. Most prey is swallowed underwater, but larger or spiny prey is brought to the surface to be thrashed and softened before swallowing.
Cormorants frequently bathe, preen and oil their feathers to maintain their waterproof condition. They are often seen roosting with their wings spread. This not only dries their feathers, but also helps warm or cool the birds as needed.
Because pelagic cormorants are one of the least social cormorants, their numbers and habits don’t cause conflicts with people that sometimes arise in other places with different cormorant species. Some species congregate in huge numbers and are seen as pests, competing with humans for fish and killing vegetation or fouling the landscape with acid excrement beneath their roosts.
In our region, pelagic cormorant eggs are a valued subsistence resource and are collected along with other seabird eggs from nesting cliffs in the spring.
Look for these sleek, black, longnecked birds flying and diving along our coastal waters through October, sometimes even into November. And if you spend a little time watching them roosting on a rocky shoreline, you might catch one of their many comical facial expressions!