The Black Guillemot (Cepphus grylle): Jewel of the Rocky Coasts

A Black Guillemot in summer plumage, showing its black body, white wing patches, and bright red feet. — 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. 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)

Unlike its relatives that gather in large, boisterous colonies on towering cliffs, this bird opts for a more serene existence, nesting in smaller groups along rocky coastlines, islands, and even in the walls of harbors. Its stunning seasonal plumage transformation and eye-catching red features make it a beloved sight for coastal birdwatchers. It is also a cousin of the Common Murre.

Our Ornithologist's Tip

By the Les-Oiseaux.com team, published on July 30, 2025

My personal advice: To find Black Guillemots, ignore the huge seabird cities. Instead, scan the jumbles of boulders and low cliffs right at the water's edge. They are often seen in pairs or small groups, bobbing on the water close to shore. In summer, their bright red feet are a dead giveaway as they paddle.

Listen for their call – a surprisingly faint, high-pitched whistle that sounds like a mouse. It's a subtle sound that doesn't carry far over the waves. They are creatures of habit, often returning to the same nesting crevice year after year, so if you find a pair, be sure to revisit the spot.

Identifying the Black Guillemot

Key Features

The Black Guillemot undergoes a complete transformation between seasons. In summer, its plumage is entirely black, except for large, obvious white patches on the upper wings. Its most striking features are its vibrant coral-red feet, legs, and the inside of its mouth (gape), which contrast with its slender black bill. In winter, the body becomes mostly white, with a pale grey head and mottled grey-and-white barring on the back, giving it a frosty appearance. The white wing patches remain year-round, helping to distinguish it even in its paler plumage from relatives like the Common Murre.

A Black Guillemot in winter plumage, showing its mostly white body and head with grey barring. — 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
Life expectancy	10 – 18 years	10 – 18 years	Up to 29.9 years

These figures confirm the Black Guillemot as a distinctive medium-sized seabird, well-adapted to its coastal environment.

Call and Behaviour

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.

0:00 / 0:00

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 is largely a resident bird, especially in the more temperate parts of its range like the UK and Ireland, though populations from the high arctic will migrate south in winter as sea ice advances. It nests on rocky shores, islands, and low cliffs, always close to the sea where it forages in shallow waters.

Distribution Map

The map below shows the Black Guillemot's range. It is present all year in many coastal areas of the North Atlantic (purple), and uses more northerly Arctic regions for breeding during the summer (orange).

Present all year (Resident)

Breeding range

Conservation Status

Globally, the Black Guillemot is listed as a species of Least Concern by the IUCN due to its very large population and wide distribution. In the UK, it is on the Green List of conservation concern. While the overall population is considered stable, local populations can be vulnerable to threats such as predation by invasive species like American mink, oil pollution, and the impacts of climate change on food availability.

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.