The Black Guillemot (Cepphus grylle): Jewel of the Rocky Coasts
The Black Guillemot, or 'Tystie', is unmistakable in summer with its smart black plumage and vivid red feet.
An Introduction to a Coastal Charmer
The Black Guillemot (Cepphus grylle), affectionately called the 'Tystie' in Scotland, is a medium-sized seabird belonging to the auk family, just like its close relatives the Razorbill and the Atlantic Puffin. It typically measures between:
Length: 30 to 38 cm (approx. 12-15 inches)
Wingspan: 49 to 59 cm (approx. 19-23 inches)
Weight: 320 to 550 grams (approx. 11.3 oz to 1 lb 3.4 oz)
What makes it unique is its black plumage, standing out with a highly visible white wing patch, often dubbed its "mirror", along with its strikingly red feet. Unlike many other auks that prefer to gather in large colonies, the Black Guillemot opts for isolated nests in pairs or small, scattered groups. It's a skilled diver that feeds in shallow coastal waters. It is also a cousin of the Common Murre.
Our Ornithologist's Tip
By the Les-Oiseaux.com team, published on August 1, 2025
My personal advice: The Black Guillemot is a fascinating coastal seabird, but sometimes confused with other auks like the Razorbill. To identify it for sure, here are two key elements to observe:
Plumage and vivid colors: In breeding plumage, it is entirely black except for a large, very visible white patch on each wing, its "mirror". Its legs, feet, and the inside of its mouth are a striking coral red, a detail often visible when it calls or defends itself. In winter, its plumage becomes mostly white and grey, but the white wing patch persists.
Behavior near coasts: Unlike other seabirds that prefer the open sea, the Black Guillemot stays close to the coast. It dives to feed in shallow waters, often near the seabed. Watch it swim underwater where its white patches and red feet make it surprisingly visible from the surface.
By paying attention to these details, you won't miss recognizing this superb bird during your observations by the sea.
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Identifying the Black Guillemot
The identification of the Black Guillemot varies considerably between its summer and winter plumages.
Breeding plumage (summer): The adult is almost entirely black or brownish-black, with the exception of a large, oval white patch on the upper side of each wing. Its slender, pointed bill is black, but the inside of its mouth is vermillion red, a characteristic often visible during displays. Its webbed feet are a striking red.
Non-breeding plumage (winter): In winter, the bird becomes much paler. The head and underparts whiten, while the back and top of the head become "salt and pepper," mottled with grey and white. The large white patch on the wing, however, remains a constant identification feature.
Juvenile: The young guillemot resembles the adult in winter, but its plumage is generally duller, and the white patch on its wings may be mottled or bordered with brown.
In winter, the Black Guillemot's plumage changes to a frosty white and grey, but the white wing patches are always visible.
Scientific Dimensions and Records (Black Guillemot)
Characteristic
Male
Female
Record / Average
Length
30 – 38 cm
30 – 38 cm
30 – 38 cm (adults)
Weight
300 – 485 g
300 – 485 g
300 – 485 g (adults)
Wingspan
49 – 58 cm
49 – 58 cm
49 – 58 cm
Flight speed
≈ 20 km/h
≈ 20 km/h
≈ 20 km/h (estimation)
Life expectancy
10 – 18 years
10 – 18 years
Up to 29.9 years (in wild)
These figures confirm the Black Guillemot as a distinctive medium-sized seabird, well-adapted to its coastal environment.
Not to be confused with...
Common Murre
The Common Murre (Uria aalge) is larger than the Black Guillemot. In breeding plumage, it is primarily brownish-black with a white belly and lacks the large white wing patch ("mirror") of the Black Guillemot. Its bill is longer and more pointed. In winter, the Common Murre has a white throat and cheeks, but the back remains dark.
The Razorbill (Alca torda) is also larger, with a more robust body and a distinctly thicker, laterally compressed bill featuring a visible transverse white line. It is black above and white below, and also does not display the white "mirror" on the wing.
The Black Guillemot's call is not what you might expect from a seabird. It's a high-pitched, thin whistle or a mouse-like squeak, often given near the nest site. It is generally a quiet bird away from its breeding grounds. During defensive or courtship behaviors, it may open its bill to expose the vivid red interior while emitting these whistles.
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Behaviourally, they are skilled divers, propelling themselves underwater with their wings to hunt for fish and crustaceans near the seabed. They typically forage in shallow, inshore waters. Unlike the densely packed colonies of their relatives, Black Guillemots are more solitary, nesting in pairs or small, loose groups in rock crevices, under boulders, or in man-made structures like piers.
The Crucial Difference: Black Guillemot vs. Common Guillemot (Murre)
The name "guillemot" can be confusing. Here is a simple table to distinguish the Black Guillemot from the much more numerous Common Guillemot (known as Common Murre in North America).
Feature
Black Guillemot
Common Guillemot (Murre)
Summer Plumage
All black with large white wing patches
Dark brown/black back and head, with white underparts
Winter Plumage
Mostly white with grey-black barring
Similar to summer, but with white on the face/throat
Feet
Bright coral-red
Dark and rarely visible
Bill
Short and slender
Longer, more pointed "dagger-like" bill
Nesting Habit
Solitary or in small groups in rock crevices
Huge, dense colonies on open cliff ledges
Habitat and Distribution
The Black Guillemot is a circumpolar species, found along the coasts of the North Atlantic and Arctic Oceans. It prefers nesting sites offering cavities, such as scree at the base of cliffs, rock fissures, or even under large rocks. Unlike its cousin, the Common Murre, which nests on exposed ledges, it seeks shelter to lay its eggs. Northern populations are migratory, moving south to find ice-free waters in winter, while many others are year-round residents.
Distribution Map
Present all year (Resident)
Breeding range (Nesting)
Diet
The Black Guillemot's diet consists mainly of small, bottom-dwelling fish, such as butterfish, blennies, and sand eels, as well as crustaceans and other marine invertebrates. It is an excellent diver that uses its wings to propel itself underwater, hunting its prey in generally shallow coastal waters, usually less than 40-50 meters deep. It can remain submerged for over a minute. Small prey are often swallowed directly underwater, while larger ones are brought to the surface.
Reproduction
The Black Guillemot reaches sexual maturity around 3 or 4 years of age and generally forms lifelong pairs. The breeding season extends from May to June. The female lays one or two eggs directly on the ground in a rock crevice, a burrow, or under a rock, without building a true nest, although small pebbles may be used.
Both parents take turns incubating the eggs for about 23 to 29 days. After hatching, both adults feed the chicks, bringing them up to 20 fish per day, one by one, held crosswise in the bill. The young leave the nest after 30 to 40 days, often before they can fly, and then become independent.
Conservation Status
Globally, the Black Guillemot is listed as a species of Least Concern (LC) by the IUCN, and its global population is considered stable, or even increasing in some regions like North America. Its total population is estimated between 400,000 and 700,000 individuals.
However, the species remains vulnerable to oil pollution, entanglement in fishing gear, and introduced predators at its nesting sites. Its dependence on Arctic sea ice for overwintering and feeding in the northern part of its range also makes it sensitive to the effects of climate change.
Frequently Asked Questions (FAQ)
Why is it called a 'Black' Guillemot if it's white in winter?
The name comes from its stunning, all-black breeding plumage in summer, which features a bold white wing patch. Its winter plumage is dramatically different, appearing mostly frosty white with grey barring on the back to blend in with the icy winter seas.
What makes the Black Guillemot's feet so red?
The Black Guillemot's bright coral-red legs, feet, and mouth lining are key identification features, especially in summer. The vibrant colour is part of its breeding display and makes it one of the most distinctive auks. In winter, the red becomes much paler.
What do Black Guillemots eat?
Their diet consists mainly of small, bottom-dwelling fish like butterfish, blennies, and sculpins, as well as crustaceans and marine worms. They are skilled divers and hunt in shallow coastal waters, using their wings to 'fly' underwater.
