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Black Guillemot Life History



Black Guillemots breed along rocky ocean coasts and islands, where they seek out crevices in the rocks for nesting. During the breeding season they forage in shallow marine waters near the nest, usually waters less than 100 feet deep. After breeding, some remain near their nesting sites and forage in shallow open water or at the edge of ice that forms along shorelines. Other individuals disperse far from nesting areas. During winter, many Black Guillemots forage far from shore, at the edge of pack ice or in openings in the ice called polynyas.

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Black Guillemots eat mostly small fish, with smaller quantities of invertebrates such as crabs, worms, and mollusks. To take prey, they dive beneath the water, propelling themselves with the wings and steering with the feet. With a quick jab of the bill, they capture prey near the bottom, from between rocks, in the water column, and from below sea ice. They swallow small prey underwater and bring larger items to the surface to process (soften) in the bill before swallowing whole. Prey includes pollock, Arctic cod, grubby, rock gunnel, northern sandlance, radiated shanny, sculpins, blennies, sea scorpions, herrings, pricklebacks, and pouts. They also eat a remarkable array of other marine creatures, including sponges, jellyfish, ctenophores (such as comb jelly), bristleworms (polychaetes), segmented worms (annelids), squid, mollusks (such as sea snails), and small crustaceans (amphipods, decapods, copepods, euphausiids, mysids, cumaceans, and barnacles).

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Nest Placement


Nests above the high tide mark on rocky coasts, usually in cliff crevices or gaps between boulders; also holes under tree roots, old puffin burrows, or under jetsam.

Nest Description

Many pairs lack true nests and lay eggs directly on the ground. Some make very basic nests of pebbles, seaweed, feathers, bones, and shells. Nests and cavities vary greatly in size.

Nesting Facts

Clutch Size:1-2 eggs
Egg Description:

Dull white to pale green, boldly marked with dark spots and blotches.

Condition at Hatching:

Covered with black down and can move about on land.

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Surface Dive

Black Guillemots usually form monogamous bonds that last for many nesting seasons. In spring, pairs return to the breeding grounds and commence courtship near last year's nest site. The male circles the female at sea, swimming around her and calling. On land, the male also circles her and vocalizes, pointing the bill downward and raising the scarlet feet conspicuously as he marches. The female then circles the male, crouching instead of high-stepping as she goes. When they are feeding young, adults take turns staying at the nest and foraging. As they exchange places, the male and female move their heads side to side, call, and touch bills together in what ornithologists call a greeting ceremony. Chicks leave the nest 4–8 weeks after hatching, usually unaccompanied by their parents. Black Guillemots often nest in areas with few other guillemots or alcids near, except in the Arctic where they may form colonies up to several thousand pairs.

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Low Concern

Partners in Flight estimates a global population of 750,000 breeding birds and rates the species a 10 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. In 2002, the North American Waterbird Conservation Plan estimated a North American population of 100,000–200,000 breeding birds. Because of the species' remote breeding habitat, it's difficult to determine whether Black Guillemot numbers are rising, stable, or falling. Black Guillemots forage mostly close to shore, which tends to expose them to more pollution (stored in feathers, body tissue, and eggs) than more oceangoing seabirds. These pollutants include mercury, PCBs, pesticides, and crude oil residues. Because of this tendency, scientists have used Black Guillemots as a tool to monitor local pollution in some areas. High levels of contamination are sometimes associated with nest failures. Oil spills can kill Black Guillemots. Global climate change is also likely to affect Black Guillemots, particularly by changing ocean currents, temperatures, and fish distributions.

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Butler, Ronald G. and Daniel E. Buckley. (2002). Black Guillemot (Cepphus grylle), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

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.

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