- 11.8–12.6 in
- 20.5–22.8 in
- 11.3–17.1 oz
- Guillemot à miroir (French)
- The Black Guillemot carries fish crosswise in its bill. Some adults seem to show a preference for the direction in which the fish heads point; this "handedness" may be related to the selection of foraging sites.
- The Black Guillemot can stay underwater for up to 2 minutes and 20 seconds.
- The Black Guillemot shows a considerable amount of geographic variation in the amount of white in its winter plumage. Higher-latitude populations show more white background color than do southern populations, and can be nearly pure white with black wings.
- The Black Guillemot breeds colonially, with different densities at different sites. Colonies tend to be smaller in the southern portion of breeding range, perhaps because prey is more widely distributed. In the high Arctic, where food is more concentrated, some colonies have 2,000-10,000 pairs.
- The oldest Black Guillemot recorded was over 27 years old when it was recaptured and rereleased during banding operations in Alaska.
Nests on rocky coastlines; forages in near-shore waters.
Fish, crustaceans, and marine invertebrates.
- 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.
Nest may consist of shells, pebbles, seaweed, and bones, or egg may be laid directly on rock with no nest material at all. Placed on rocky coast, often under overhang or boulder, or in a cavity.
In courtship display, male stands upright, points bill down, and walks around female with exaggerated steps.Shows various lunges, turns of the head, and other posturing in territorial interaction with other Black Guillemots.Dives under water to capture prey, using its wings to swim. Small prey swallowed under water; larger items brought to surface.
Lack of accurate census data makes determination of population trends difficult. The North American Waterbird Conservation Plan estimates a North American population of 100,000-200,000 breeding birds, and this species rates a 9 out of 20 on the Continental Concern Score. They are listed as a Species of Lowest Concern, and are not on the 2014 State of the Birds Watch List. The Black Guillemot is more susceptible to ingestion and biomagnification of marine pollution than other alcids because it takes prey from shallow water or at the sea floor. Studies have shown accumulation of mercury, pesticides, and crude oil residues in body tissues and eggs. Oiling of feathers from spills at sea usually results in death. Global warming may also affect populations.
- Butler, R. G., and D. E. Buckley. 2002. Black Guillemot (Cepphus grylle). In The Birds of North America, No. 675 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
- North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014 Report. U.S. Department of Interior, Washington, DC.
- USGS Patuxent Wildlife Research Center. 2015. Longevity records of North American Birds.
- Waterbird Conservation for the Americas, Technical Services Committee, Waterbird Conservation Council. 2006. Status Assessment Spreadsheet - Factor Scores and Categories of Concern for Colonial Waterbirds.