Sooty Shearwater

The Sooty Shearwater, Ardenna grisea, is a medium-large member of the seabird family Procellariidae. Known in New Zealand as tītī and colloquially as muttonbird, this species is cloaked in a chocolate-brown plumage, which under certain light reveals a silvery sheen along the center of the underwing.

Identification Tips

When observing the Sooty Shearwater, one notes its powerful and direct flight, with wings held stiff and straight, reminiscent of a miniature albatross. Its dark plumage is the key to its identification; however, in dim conditions, it may appear uniformly black. The bird's "shearing" flight, where it dips from side to side on stiff wings with minimal wingbeats, is characteristic.

Habitat

These birds are pelagic, spending the majority of their lives at sea. They come ashore only to breed on small islands in the southern oceans.

Distribution

The Sooty Shearwater breeds on islands across the south Pacific and south Atlantic, with significant populations around New Zealand, the Falkland Islands, and Tierra del Fuego. They are known for their remarkable long-distance migrations, traveling vast distances across the Pacific and Atlantic Oceans.

Behaviour

Sooty Shearwaters are solitary migrants, often associating only opportunistically with others of their kind. They are adept divers, plunging to depths of up to 68 meters in search of prey, though they more commonly feed at the surface, sometimes capitalizing on the disturbances caused by whales or fishing boats.

Song & Calls

While on breeding grounds, Sooty Shearwaters are vocally active, emitting cooing and croaking sounds that resonate through their colonies.

Breeding

Breeding begins in October, with a single white egg laid in a burrow lined with plant material. These burrows are visited exclusively at night to avoid predators. The incubation period lasts approximately 54 days, followed by a chick-rearing period of 86 to 109 days.

Similar Species

The Short-tailed Shearwater presents the most challenge in differentiation, as it shares the all-dark plumage and is nearly indistinguishable at a distance.

Diet and Feeding

Their diet consists primarily of fish and squid. They have been observed following marine mammals and fishing vessels to feed on disturbed prey or discarded scraps.

Conservation status

The Sooty Shearwater is currently classified as Near Threatened. Declines in population have been noted, and recent years have seen record-low catches in traditional harvests, indicating potential stress on the species.

Inspiration for Hitchcock's The Birds

An unusual event involving disoriented Sooty Shearwaters in 1961 in California is believed to have partly inspired Alfred Hitchcock's iconic film "The Birds." The birds' erratic behavior was later attributed to poisoning from toxic algae, linked to environmental changes in the area.