Morus bassanus



This is the biggest seabird in the region and it is quite distinguishable from other species. When it flies, its body is cigar-shaped, its wings long, slender and pointed. The sexes are similar; this bird has a long neck, a narrow bill which comes to a point, and its tail is pointed too. Adult birds are mostly white, though the tips of its wings are black and it has a brownish-yellow tinge to its head which pales come winter. Juvenile birds are a dark brown-grey with white speckles.


Except when nesting, this is exclusively a marine bird, though winds may cause it to fly near to headlands. Majority of colonies in the region are in the north and west of Britain and Ireland. Nesting sites are islands or cliffs exposed to the sea.


When flying, it flaps its wings with power than glides with ease; they can dive for fish from surprising heights, and will often gather in large numbers when a good feeding spot is found. Birds have been known to steal food from one another and from other species. Nests in expansive colonies, usually on inaccessible sea cliffs.


Diet is predominately fish, particularly herring and mackerel, but also caplin, sprat and sand eel.


Nests are made from floating sea plants such as seaweed, stuck together with the bird's droppings; the nest is added to each year. A single egg is laid and parents both incubate it using their feet; egg hatches after 44 days. Both parents brood and feed the chick until about 90 days, when they desert the chick; it remains in the nest hungry for about 10 days, then takes to the ocean where it begins to fish after about 2 to 3 weeks.


Immature birds leave their colonies in August and September and make their way to the African coast; some adults make the journey too. Most birds spend winter further north, and others remain in the region for the whole year. Approximately 220 000 pairs breed in the UK and 3 000 in Ireland; this is more than 60% of the world population.

Observation Tips

The time between April and September provides the most opportunity to see this bird on the ocean. Breeding colonies in Yorkshire and Shetland are worth a visit too, and the best close-range encounters occur at the Bass Rock colony.


When feeding, may utter a crackly call, while nesting colonies are noisy with growls and grating calls.
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