Manx Shearwater

The Manx shearwater (Puffinus puffinus) is a medium-sized member of the seabird family Procellariidae. It exhibits a distinctive "shearing" flight pattern, gliding gracefully over the ocean's surface with stiff wings. The bird's appearance alternates between black and white as it dips from side to side, with the black upper parts and white undersides becoming visible in turn.

Identification Tips

Adult Manx shearwaters measure 30–38 cm in length with a wingspan of 76–89 cm and weigh between 350–575 g. In flight, they present a cross-like silhouette, with wings held at a right angle to the body. This species is characterized by its contrasting dark upperparts and white underparts, which are especially noticeable as the bird banks and turns while flying low over the sea.

Habitat

Manx shearwaters are marine birds, typically flying within 10 meters of the sea surface. They nest in burrows on small islands, which they visit exclusively under the cover of night to avoid predators.

Distribution

This species breeds in the North Atlantic, with colonies found in the United Kingdom, Ireland, Iceland, the Faroe Islands, France, the Isle of Man, the Channel Islands, the Azores, Canary Islands, and Madeira. During the non-breeding season, they migrate to the South Atlantic, wintering mainly off the coasts of Brazil and Argentina.

Behaviour

Manx shearwaters are social and gregarious, often seen in large flocks during migration. They are known for their longevity, with one individual recorded at over 55 years of age. At sea, they are typically silent, but their breeding colonies are a cacophony of calls at night.

Song & Calls

The vocalizations of Manx shearwaters are mainly heard during nocturnal visits to their nesting burrows. Their calls are a series of raucous croons, howls, and screams, with the male's call including clear ringing and shrieking tones that differ from the female's harsher sounds.

Breeding

Breeding begins in March, with egg-laying occurring in early May. Manx shearwaters are monogamous and nest in burrows, which may be reused annually. They lay a single white egg per breeding season.

Diet and Feeding

Manx shearwaters feed on small fish, crustaceans, cephalopods, and surface offal. They forage by skimming the sea surface or by pursuit diving, either alone or in small flocks. Their sense of smell is keen, aiding them in locating food over vast distances.

Conservation Status

The Manx shearwater is classified as Least Concern by the IUCN. While the population appears to be declining, the decrease is not significant enough to trigger conservation vulnerability criteria. However, human activities and introduced predators on some islands pose threats to certain populations.

Similar Species

The Manx shearwater was once considered a monotypic species, but recent studies have proposed several closely related species and subspecies, including the yelkouan shearwater, Balearic shearwater, and others. The Hawaiian and possibly Townsend's shearwaters are most closely related to the Manx shearwater.

Predators and Parasites

On land, Manx shearwaters are vulnerable to predation by large gulls, skuas, and birds of prey. Introduced mammals such as rats and cats can devastate colonies, and parasites like feather lice and fleas are common among these birds.

In Culture

The Manx shearwater has been a source of food since prehistoric times, with its oil-rich chicks being a particular delicacy. The bird's nocturnal cries have also led to associations with the supernatural in various cultures.