Audubon's Shearwater - Range and Ecology

Range and Ecology

If not split into several species, Audubon's Shearwater ranges across the Indian Ocean north to the Arabian Sea, throughout the northwest and central Pacific, in the Caribbean, and parts of the eastern Atlantic. It is a species of tropical waters; only some Atlantic populations and Bannerman's Shearwater of the Ogasawara Islands occur farther north. Unlike the larger shearwaters, adult Audubon's Shearwaters are not thought to wander much or undertake great migrations, although their young birds do so before breeding, and western Indian Ocean birds may gather in large numbers at the upwelling zone in the Arabian Sea.

It is adaptable as regards its preferred marine habitat; it can be found in pelagic, offshore and inshore waters. It feeds in a variety of methods, mainly diving out of flight, plunging underwater from a swimming position, and picking up food less than a bill's length underwater while "pattering" as if it were walking across the waves. It eats small fish, squid and planktonic crustaceans. Unlike other shearwaters, it is not commonly a ship-follower, though it may attend small fishing boats; it is also sometimes met with as part of a mixed-species feeding flock.

The species is colonial, nesting in small burrows and crevices in rocks and on earthy slopes on atolls and rocky islets. The breeding season varies according to location and subspecies, but how precisely is not very well-studied. Both parents share the responsibility of incubating the single white egg (measurements of 52.5 by 36.2 mm and a weight of 37 g have been recorded for one specimen of average size), each incubating for periods of 2 to 10 days until the egg hatches after 49–51 days of incubation. The nestlings are brooded for half a week to one week, after which time the parents will leave it mostly alone in the burrow and spend most of their time foraging and feeding their voracious offspring, which become very fat. Time from hatching to fledging is 62–75 days. Audubon's Shearwaters take about 8 years to reach breeding age. As typical for Procellariiformes they are long-lived for their size, one bird ringed as an adult was still alive 11 years later; it must have been more than 15 years old at that time.

While some small populations are threatened, the species as a whole (in the present sense, i.e. unsplit) is not considered to be globally threatened.