Sooty shearwater  (Puffinus griseus)

Classified as Near Threatened (NT) on the IUCN Red List (1).

This large, slender shearwater (4), with dark grey-brown plumage (5), flies effortlessly over the ocean with its long, narrow wings (4). The wings have a silvery lining (5), and a patchy white underside which may be conspicuous as it flies over the sea (4). Indeed, shearwaters are named for the way in which the wings, held stiff and motionless, skim the water’s surface as they glide fast and low over the waves (7). Its long, blackish-grey bill has (4), like other shearwaters, a hooked tip and sharp blades, enabling it to efficiently handle slippery fish prey (6). Two tubular nostrils are situated on the upper bill, a unique feature of the Procellariiformes, a group of birds which includes the shearwaters, albatrosses and petrels (6). Infrequently heard in flight, the sooty shearwater is a noisy bird when ashore; its most common calls are a der-rer-ah or coo-roo-ah (3).

The sooty shearwater has an exceptionally wide distribution, being found in most major oceans except for northern parts of the Indian Ocean (3). It breeds on islands off New Zealand, Australia and southern Chile, as well as on the Falkland Islands (8).

Shearwaters are oceanic birds, typically found far from land (6), apart from during the breeding season when the sooty shearwater can be found on islands and headlands (8).

Most of the sooty shearwater’s life is spent out at sea, flying fast over the ocean with rapid wingbeats, or gliding low over the water’s surface (4). Feeding mostly on small fish, shrimp and other crustaceans, squid and jellyfish (2) (3), the sooty shearwater may snatch its prey from the ocean surface or plunge, from flight, into the water, and pursue its prey underwater. Propelling itself though the water with powerful beats of its wings, the sooty shearwater is known to reach depths of 67 metres (3).

Sooty shearwaters arrive at their breeding colonies at the end of September or very early October, with egg laying, at least in New Zealand, taking place between mid-November and early December (3). Burrows, measuring up to three metres long, are dug into the ground, under tussock grass, low scrub, or Olearia forest (3). Like all shearwaters, albatrosses and petrels, sooty shearwater females lay just a single egg into this burrow (6), which is then incubated for around 53 days (3). The chick hatches around the middle of January (3), and is then fed by both parents, who spend their days foraging at sea, returning at night to feed their chick. These night time visits are somewhat boisterous, with the parents crashing through the trees and landing on the island with a loud thump (2). At 97 days of age, in late April or early May, the chick fledges and leaves its nest to head out to sea. Sooty shearwaters generally start breeding at the ages of five to seven (3). They typically mate for life (2), attracting a partner through a duet of courtship calls and gentle mutual nibbling (3).

Upon the completion of breeding, sooty shearwaters commence their impressive migration north. From New Zealand, this bird travels to the regions off Japan, Alaska or California, before returning to New Zealand for the subsequent breeding season. Electronic tracking of this species has revealed that the sooty shearwater undertakes the longest migration of any animal tracked to date (9). Travelling in a figure-eight pattern across the Pacific Ocean, this small but intrepid bird covers an astounding 65,000 kilometres. Undertaking this great journey allows the sooty shearwater to exploit the greater abundance of prey found in the North Pacific at that time of the year (9).

Despite being a common species, the declines observed in populations of sooty shearwaters are of concern (8). Several factors have been cited as the reasons behind these declines, including hunting, fisheries and possibly climate change (8). In southern New Zealand, young sooty shearwaters are hunted by native Maori for food and oil, with around 250,000 young birds thought to be taken from their burrows each year (2). The sooty shearwater is also impacted by longline fisheries (8), a practice which is responsible for the deaths of large numbers of seabirds worldwide (10). This fishing method involves a single line up to 130 kilometres long, with thousands of baited hooks attached to it, being pulled behind a boat. Sooty shearwaters, foraging in the ocean, try to eat the bait from the line as it is set behind the boat, but instead swallow the hooks and are dragged under and drowned (11). Finally, it is thought that this species is vulnerable to changes in their food supply, which may result from either commercial fisheries, or global climate change (2).

A number of the sooty shearwater’s breeding grounds are protected (8); for example Snares Island, New Zealand, is a National Nature Reserve and forms part of the New Zealand Subantarctic Islands World Heritage Site (12). Efforts by conservation organisations to save albatross from dieing on longline fishing hooks will also benefit the sooty shearwater (11). Numerous devices can be used to prevent these unnecessary deaths; a study which examined the use of one such device, an integrated weight so that the longline sinks out of the bird’s reach faster, revealed its effectiveness in reducing the mortality of sooty shearwaters (10).

View information on this species at the UNEP World Conservation Monitoring Centre.

For further information on the threat of longlining and what can be done to save seabirds see:

• Save the Albatross:
  www.savethealbatross.net

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org