Common Guillemot: where and when to see them

The common guillemot is a densely colonial seabird of cool northern oceans, known as the common murre in North America. Its upright posture, dark upperparts and white belly can make a crowded breeding ledge resemble a miniature city. Unlike nest-building seabirds, it lays a single egg directly on rock. Large colonies are spectacular, but their fortunes depend on nearby fish supplies and can change sharply during marine heatwaves or food shortages.

Size

38-43 cm long

Weight

0.8-1.2 kg

Lifespan

15-25 years

Status

Least Concern

Breeding adults occupy narrow cliff ledges in close contact with neighbours, recognising their mates and young amid intense noise and movement. Both parents incubate and bring fish to the chick. Before it can fly, the youngster leaves the ledge and reaches the sea, usually accompanied thereafter by its father. Outside the breeding season, guillemots disperse over marine feeding grounds and become much less concentrated near accessible cliffs. Pairs maintain strong site fidelity, often returning to the same ledge year after year. The 'wing-whirring' display is a common sight on ledges, involving rapid wing beats as a form of communication or territorial defense.

• Common guillemot and common murre are names for the same species.
• It lays its egg directly on a ledge without building a nest.
• The chick leaves the colony before it can fly.
• Some Atlantic birds have a white eye-ring and line, called the bridled form.

Late spring and early summer offer the clearest coastal opportunities at occupied breeding colonies in Scotland and Norway. Exact timing becomes later toward the north and varies annually. After chicks depart, apparently suitable cliffs can empty quickly, while offshore birds remain difficult to observe from land. Prime viewing from cruise ships or shore is generally from May through July, coinciding with the busiest period of chick rearing. Even after the main departure, smaller numbers of prospecting or failed breeders may linger at colonies into August.

Breeding habitat consists mainly of steep sea cliffs, rock stacks and offshore islands with secure ledges. Feeding takes place in surrounding shelf waters. Outside nesting months, birds can occur well offshore, though storms and prey movements sometimes bring them near coastal viewpoints. Though typically nesting on cliffs, some populations may use flat, low-lying islands where predators are absent. During the non-breeding season, they inhabit a wide range of pelagic waters, often gathering in large rafts on the open sea.

Small schooling fish, including sandeels, sprats, herring and capelin, dominate where available. Adults pursue prey beneath the surface using their wings for propulsion. Chicks usually receive individual fish carried lengthwise in the bill, making food deliveries visible from distant colony viewpoints. Guillemots are opportunistic feeders, adjusting their diet based on local prey availability and abundance. Their efficient underwater hunting makes them highly adapted to capturing fast-moving marine prey, essential for sustained energy during the breeding season.

Common name

Common Guillemot

Scientific name

Uria aalge

Animal group

Birds

Size

38-43 cm long

Weight

0.8-1.2 kg

Lifespan

15-25 years

Status

Least Concern

Identification

Its slender, pointed bill separates it from razorbill, while the thicker-billed Brünnich's guillemot has a pale line along the bill edge. Their plumage is dark brown-black above and white below, with a sharp demarcation between the two colors. In winter, adults develop a white stripe behind the eye, a useful field mark that distinguishes them from their summer appearance.