Black Guillemot

Overview

The Black Guillemot (Cepphus grylle), affectionately known in Shetland, Orkney, and throughout northern maritime folklore as the ‘Tystie,’ is a charming, medium-sized circumpolar alcid native to the rocky coasts and icy waters of the Arctic and subarctic North Atlantic. Instantly recognizable in breeding plumage by its glossy, coal-black body, large oval white wing patches, and vivid, eye-popping scarlet-red legs, feet, and mouth lining, this charismatic seabird is a familiar presence along northern harbors and rocky sea cliffs. Operating as an agile, wing-propelled underwater diver, it plays a vital role as a benthic inshore meso-predator across northern marine ecosystems.

Unlike its colonial cliff-dwelling relatives like murres and razorbills, which crowd open rock ledges by the thousands, the black guillemot is a secretive, small-colony or solitary nester that deposits its eggs deep within sheltered boulder crevices, talus screes, and coastal rock fissures. It maintains an extraordinarily intimate association with coastal shallow waters, rarely wandering far out to pelagic ocean waters even during the depths of winter. Thriving along the edges of pack ice, polynyas, and rocky shores, the species acts as an essential bioindicator of benthic inshore fish communities and Arctic coastal biodiversity.

Biology and Physical Characteristics

Morphologically, Cepphus grylle is built for dual-medium locomotion: propelled through the air by rapid, direct wingbeats and flying underwater with effortless, hydrofoil-powered wing strokes. Its breeding plumage is unmistakable: a velvety, soot-black body illuminated by a large, oval white patch covering the upperwing coverts, and a slender, straight black bill that opens to reveal a startling, bright coral-red mouth lining used in courtship displays. Its legs and webbed feet are a brilliant, luminous vermilion-red, providing vivid color flashes as the bird paddles across dark northern waters.

In autumn, the bird undergoes a complete pre-basic molt into a frosty, camouflage winter plumage dominated by white underparts, a pale grey-barred back, and a mottled white head that blends into floating sea ice. Its wing bones are dense and flattened, and its plumage is exceptionally compact and waterproofed with rich uropygial oils that trap an insulating layer of warm air against the skin. Its eyes possess flattened corneas that optimize optical refraction underwater, allowing it to spot cryptically colored benthic fish hiding among tangled kelp fronds.

Behavior and Ecology

Black guillemots are strictly coastal foragers that hunt in shallow nearshore waters, typically at depths of 10 to 30 meters, within a few kilometers of their nesting sites. When diving, the bird submerges smoothly, using its wings to ‘fly’ downward along the seabed, probing into rocky cracks and kelp beds for bottom-dwelling fish—particularly rock gunnels (Pholis gunnellus), blennies, sculpins, and sandeels—before returning to the surface with a single fish held crosswise in its bright red bill.

During the spring breeding season from May to July, pairs engage in delightful courtship displays along calm coastal waters, swimming in tight circles, bobbing their heads, and flashing their scarlet mouth linings while uttering high-pitched, piping whistles that sound remarkably like tiny songbirds. Unlike other alcids that lay only a single egg, the black guillemot regularly lays a clutch of two heavily blotched eggs inside a dark rock crevice or stone harbor wall. Both parents share incubation for approximately 28 to 32 days, and jointly feed the chicks for nearly six weeks until the fledglings flutter down to the sea under the cover of darkness.

Conservation and Human Impact

The Black Guillemot is classified as Least Concern on the IUCN Red List of Threatened Species, supported by a large global population estimated at between 400,000 and 700,000 individuals distributed across the vast, remote circumpolar coasts of North America, Greenland, and Eurasia.

However, localized populations face severe regional threats, particularly from invasive mammalian predators. Because black guillemots nest at or near ground level in low boulder piles and rock crevices, introduced American mink (Neovison vison) and feral cats can easily enter burrows, devouring entire clutches of eggs, chicks, and brooding adults, which has caused local extirpations across islands in Scotland, Sweden, and Finland. Chronic oil pollution, entanglement in coastal monofilament gillnets, and rising water temperatures that alter benthic prey assemblages represent persistent conservation concerns that require continued pest eradication on offshore nesting islands.

Interesting Factoid

Unlike almost all other members of the auk family—such as puffins and murres, which can only raise a single chick per year—the black guillemot regularly lays and successfully rears two chicks every summer thanks to its rich, reliable inshore diet of bottom-dwelling blennies.