Sooty shearwater

Puffinus griseus is a shearwater of the family Procellariidae, in the order Procellariiformes ^[1]. It breeds on Southern Hemisphere islands, with some 21.3 million birds in the New Zealand region alone in 1994–2005 ^[2], and after breeding it crosses the Pacific on a figure-eight route of about 64037 km ^[3]. In an at-sea census off northern and central Peru in July 2010 it was the densest seabird, at 20.73 individuals per square kilometre ^[4].

It is an abundant seabird along the coasts of the northern and southern Pacific, according to the review by Figueroa and Suazo, who give New Zealand, Australia and Chile as its breeding areas ^[4]. In the Northern Hemisphere it predominates among the seabirds of the western seaboard of North America, especially in the California Current ^[2]. Newman and colleagues recommend treating with extreme caution an estimate published by others for Guafo Island, off Chile (3.98 million breeding pairs, ±3.87 million), because it was extrapolated from sampling in a single 7 ha area and an earlier estimate gave about 200000 individuals ^[2].

In the July 2010 census (days 14 to 25), between latitudes 7°00'S and 10°59'S and 8.33 to 78.71 km from the coast, the species was present in 60.84 % of the area surveyed ^[4]. Its highest counts in Peruvian autumn and winter censuses fall between those same latitudes, and the authors attribute this to much of the population migrating to the North Pacific after breeding in the austral summer ^[4]. Most seabirds in that census were over the continental shelf, 18.52 to 46.30 km from the coast ^[4].

Using miniature electronic loggers, Shaffer's team followed birds breeding in New Zealand: each made a long stopover in one of three regions, off Japan, Alaska or California, and returned through a narrow corridor of the central Pacific ^[3]. The round trip measured 64037 ± 9779 km over 262 ± 23 days, the longest ever recorded electronically for an animal ^[3].

In transit it reached up to 910 ± 186 km per day, and the birds fed in highly productive waters of both hemispheres, diving down to 68.2 m ^[3].

It nests in burrows, in colonies ^[2]. On the main island of the Snares, Warham and Wilson found the highest density, 1.9 burrows per square metre, in the meadows, and 1.2 under the forest; assuming 75 % occupancy they estimated about 2750000 pairs on 328 ha of the two larger islands ^[5].

Off Peru, the large groups mostly flew south between 07:00 and 10:00 h and between 17:00 and 18:00 h, above all at latitude 7°S, where 4976 birds were counted, 60.29 % of the species' total in the census ^[4].

At 20.92 km from the coast, groups were seen feeding together with Sula variegata and the dolphin Delphinus capensis over a large school of fish that appeared to be anchoveta, and the species was also seen following Lagenorhynchus obscurus while it hunted anchoveta ^[4]. The authors recall that in California and South Africa it has been recorded eating other anchovies, Engraulis mordax and Engraulis capensis, and that its distribution would be set by where the cephalopods and fish of its diet concentrate ^[4].

Puffinus creatopus was recorded at latitudes 7°S, 8°S and 9°S, in groups of its own species and in mixed groups with Puffinus griseus ^[4]. At the scale of the Pacific, its annual cycle links the most productive zones of the north and the south ^[3].

On beaches of northern New Zealand, between 1961 and 1999, adult birds found dead declined by 64.4 % and fledglings by 77.7 % ^[6]. The authors name rising sea temperature and heavier harvest as possible factors, and found in their data no direct evidence of an effect of North Pacific fishing mortality or climate ^[6].

At one of the largest colonies on the main island of the Snares, the density of burrow entrances fell 37 % between 1976 and 2001 ^[2]. Fisheries bycatch has been estimated to have killed between 1.0 and 12.8 million birds from 1952 to 2001, with great uncertainty, and the threat was much reduced after the international driftnet ban of 1991 ^[2].

In Peru, Figueroa and Suazo mention birds of the species caught in the gillnets of monitored vessels; only one individual approached the census vessel, and they therefore consider catches in nets and longlines infrequent ^[4].

The Rakiura Māori harvest chicks of the species, called tītī, in April and May on the Tītī Islands near Rakiura (Stewart Island) ^[2]. The harvest was estimated at 360000 chicks per year (320000–400000), 18 % of the chicks in the harvested areas and 13 % of those in New Zealand, and 53 % of the country's breeding pairs nest on those islands ^[2].

In the July 2010 census it was counted from a survey vessel, in an area between 8.33 and 78.71 km from the coast of La Libertad, Ancash and northern Lima ^[4]. The large groups passed flying south mostly between 07:00 and 10:00 h and between 17:00 and 18:00 h, with the peak at latitude 7°S ^[4].