Brandt's Cormorant Life History

Habitat

Brandt’s Cormorants are strictly coastal birds, almost never found inland. Even along the coast, they seldom fly over land. In coastal waters they favor kelp beds and sometimes enter inlets, bays, sounds, lagoons, and estuaries. They are usually not more than 10 miles from land except during migration. In Mexico, Brandt’s Cormorants sometimes visit freshwater habitats very near the coast. This species’ largest breeding populations inhabit northern California and Oregon, where the upwelling caused by the California Current is strongest. Nonbreeding birds use the same habitats as breeding birds, but they often move to more productive areas of upwelling later in the year, after the California Current upwelling wanes. A small wintering population in southwestern British Columbia, Canada, uses bays and fjords with rocky coastlines. Most Brandt’s Cormorants rest and roost on rocky islands, coastlines, and cliffs, but they sometimes use sandy beaches as well.

Food

Brandt’s Cormorants dive from the surface and swim underwater, visually hunting fish and squid. They grasp prey in the bill, crush it, then swallow it headfirst. Depending on prey availability, they may hunt near the surface or near the bottom, as far as 230 feet down. They often forage in flocks, which may move quickly when feeding on schooling fish near the surface. The cormorants dive beside or below the school, then drive prey toward the surface for capture. Large flocks appear to feed in concert, with birds surfacing rapidly, then flying to the leading edge of the flock. These flocks often mix with other seabirds (gulls, terns, pelicans, auks, loons, grebes, shearwaters, and other cormorant species), and even California sea lions and Steller's sea lions, making for an impressive aggregation of marine life. At least 93 species of fish are recorded as prey items, including northern anchovy, sand dab, señorita, cabezon, kelp surfperch, shiner surfperch, monkeyface prickleback, rockweed gunnel, plainfin midshipman, Pacific butterfish, medusafish, Pacific herring, Pacific tomcod, and multiple species of rockfish, cardinalfish, damselfish, sculpins, and seabass.

Nesting

Nest Placement

Males select nest sites on windward slopes of rocky islands, steep cliffs, and areas of boulders.

Nest Description

Males collect (sometimes steal) nesting material, and both male and female arrange it constantly during incubation. Nests are circular bowls of grass, moss, weeds, sticks, marine algae, and bits of driftwood (less often feathers). Nests measure on average 13.8 inches across and 6.1 inches tall, with interior bowl 7.8 inches across and 3.5 inches deep.

Nesting Facts

Behavior

Male Brandt’s Cormorants usually arrive before females in nesting areas and claim small nesting territories on rocks or cliffs. The territories are tiny, often just 3 feet from the next neighbor, but defended vigorously with threat displays (including raised wings and snakelike neck movements), pecks, shoving matches, and wing flapping. Males begin adding nest material to the site before they have a mate and in some cases even before females arrive. Males advertise to females by pointing the bill skyward (to show off the blue skin of the throat) or by waving the wings. In this display, the male leans forward, cocks and spreads the tail, thrusts the head and neck over the back, and raises the partly open wings, fluttering them and pumping the head up and down. Females also sometimes fight other females that have taken a past nest site. Pairs maintain their bond usually just for one season. They greet each other at the nest with displays, including pointing the bill at the sky, a “gape” display in which they inflate the blue skin of the throat and cock back the head, and a display in which the females grasp the male’s bill (containing nesting material) and the two sway with bills locked, gradually placing the material in the nest. Both sexes share incubation and chick-rearing duties. Brandt’s Cormorants are strong divers, leaping up clear of the water before entering, and excellent swimmers. Unlike other cormorant species, Brandt’s does not spend long periods holding a spread-wing posture to dry the wings.

Conservation

Brandt's Cormorant populations appear to be in decline. Global breeding population estimates range from 151,200 in 2002 (Waterbird Conservation for the Americas) to 100,000 in 2017 (Partners in Flight). Partners in Flight rates the species a 14 out of 20 on the Continental Concern Score and includes it on the Yellow Watch List for species with restricted ranges. Although it is illegal to shoot Brandt’s Cormorants, some are still shot. Oil spills and chemical pollution threaten seabirds and their marine prey species, and several major spills have killed significant numbers of Brandt’s Cormorants, which may be more vulnerable than some other seabirds because they forage in coastal areas where spilled oil concentrates. Disturbance at colonies by boaters, aircraft, humans, and dogs can result in eggs being broken or stolen by gulls, or in the permanent abandonment of the colony.

Credits

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Lutmerding, J. A. and A. S. Love. (2020). Longevity records of North American birds. Version 2020. Patuxent Wildlife Research Center, Bird Banding Laboratory 2020.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

Wallace, Elizabeth A. and George E. Wallace. (1998). Brandt's Cormorant (Phalacrocorax penicillatus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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