Black Guillemot

The Isles of Shoals off the New Hampshire coast are the southernmost breeding site in the world for the Black Guillemot. Although some colonies in the far north may contain thousands of pairs, guillemots are less gregarious than most other alcids, and tend to occur in colonies of fewer than 50 pairs. Here at the southern edge of their range, there may be only 10-15 nests each year at the Isles of Shoals.

These nests are typically located in rocky crevices, under detritus such as driftwood and abandoned fishing gear, or in burrows. The birds sometimes line these with pebbles, pieces of vegetation, or broken shells, and lay two eggs starting around late May. The eggs are incubated for about a month, and upon hatching the chicks are fed for roughly 40 days before they are ready to head to sea. Still unable to fly, they scramble down to the ocean at night and shortly thereafter leave the immediate vicinity of the colony. At this point they are completely independent of their parents and feed on their own, but aren’t capable of sustained flight for 3-4 more weeks.

Guillemots feed in relatively shallow waters, where they use their wings to swim underwater in search of fish and invertebrates on the ocean floor. Because of their preferred foraging habitat, they are the most likely alcid (the group of birds that also includes puffins) to be seen from shore in New Hampshire during the winter, when some even enter harbors or coastal coves. During the winter guillemots have molted out of their distinctive black and white plumage and resemble little gray and white blobs floating offshore. They molt back into breeding plumage starting in March and April, at which point they are also returning to their nesting sites and less likely to be seen from shore.

Because they nest out of sight and often at low densities, data on Black Guillemot populations are limited. The population in the Gulf of Maine and eastern Canada is estimated between 150,000 and 200,000, and available data suggest it is increasing.