Manx shearwater

The Manx shearwater (Puffinus puffinus) is, despite its botanical name, not a puffin or even related to the small seabirds with large bills that have that name (and are, in fact, auks). The two species do, however, share the characteristic behaviour of building nests in burrows on clifftops.

The Manx shearwater is a seabird that spends most of its life at sea, only coming ashore to breed. It takes the first part of its name from the Isle of Man, where it once bred in considerable numbers. After an absence of around 150 years the species returned in the 1970s. It is also found, during the breeding season, on other islands off western coasts of the British Isles.

The second part of the name comes from the bird’s habit of flying low over the sea, appearing to “shear the water” as it hunts for fish.

A fully-grown Manx shearwater is around 30-35 centimetres (12-14 inches) in length and with a wingspan of around 71-83 centimetres (28-33 inches). The wings are straight and slim and the bill is also long and thin.

The plumage is dark brown above and white below. This applies to both the head and body. The wing undersides are dark at the edge, presenting a sharp contrast with the white centres. The sexes are alike in appearance.

The Manx shearwater is the most common shearwater species to be seen around the British and Irish coasts and can often be seen in flocks where food is plentiful. A number of Manx shearwaters will fly in a line, rising and falling on currents of air.

They feed on fish including herrings, sardines and sprats. These are taken from close to the surface or by diving.

The Manx shearwater is one of Nature’s great navigators. It roams across the whole of the Atlantic Ocean, with many of them spending the winter off the coast of South America. However, they will unerringly return to the same burrow to breed. There was a case of a bird being tracked as it took only 12 days to reach the Welsh island of Skokholm after being taken 3,000 miles to Massachusetts, which was well outside its normal range.

Breeding take place after the birds return to their nesting sites between late February and April. This takes place in colonies on island clifftops. It sometimes happens that the burrows they excavate are so close together that they collapse into each other. Alternatively, they may use existing burrows that were dug by rabbits.

A single egg is laid which is incubated by both parents, taking this duty in turns of about six days each. When born, the chick has thick downy fur which it keeps until it is ready to leave the burrow. The parents feed the chick on pre-digested fish, only doing so on dark nights. If there is bright moonlight or poor weather the chick may have to go without food for several consecutive days.

About 60 days after hatching the chick is deserted by its parents and, after a delay of eight or nine days with no food being delivered, makes its own way out of the burrow to begin an independent life.

A Manx shearwater will be ready to breed at the age of five or six and may well have a lifespan of 50 years.

Manx shearwaters are renowned for the eerie calls they make on returning to their nests at night. These have given rise to legends of the ghosts of shipwrecked sailors returning to the scene of their demise – the rocky islands on which Manx shearwaters breed have certainly been the cause of many such disasters down the centuries.

© John Welford