A mostly pelagic species, the wedge-tailed shearwater forages over large tracts of open ocean where it feeds mainly on fish, although cephalopods, crustaceans and insects may also be taken (2) (7) (9) (10). It generally feeds during the day, often aggregating in feeding flocks associated with tuna and other large predatory fish, or congregating around other seabirds, dolphins, trawlers or fishing boats (2) (9) (10).
The wedge-tailed shearwater catches its prey primarily by ‘contact-dipping’, where the bird flies close to the surface and plunges the head and neck into the water to capture prey during flight. Having seized a fish or other prey item, the wedge-tailed shearwater flips the head upwards to swallow the prey mid-flight. The wedge-tailed shearwater may also sit on the water surface to feed, and will sometimes make deeper dives, to a maximum depth of 66 metres below the surface (2) (7).
The wedge-tailed shearwater breeds between February and November in the Northern Hemisphere and September to June in the Southern Hemisphere, although the exact timing varies with location (2) (3) (10). The wedge-tailed shearwater is monogamous and generally returns to the colony in which it was born to breed, often reclaiming the same nest site from season to season (2) (3) (12) (13).
The nest site is selected by both the male and female wedge-tailed shearwater as part of the courtship ritual. Nests are usually close to sea level, in burrows in sand or soil. It may also nest in rock crevices and caves, or will sometimes nest on the surface under dense vegetation (2) (1). Both adults contribute to the excavation of the burrow, digging using the bills and feet to loosen, scrape and remove the soil (2) (3). The first part of the burrow generally slopes downwards towards a nesting chamber which is often, but not always, lined with vegetation (2). Mating takes place either in or near the burrow once the nest is complete, after which both members of the breeding pair will return to sea for up to a month to forage, building up energy reserves for egg-laying and incubation (2) (3) (11) (12).
The wedge-tailed shearwater lays a single, very large white egg which is incubated for between 50 and 53 days. Both adults share the incubation duties in alternating shifts that last up to 13 days at a time, with the male generally incubating first (2) (3) (11) (13). After hatching, the chick is brooded for up to six days, after which it is left alone while the adults hunt. The chick is initially fed by the adults with stomach oil, an energy-rich, waxy oil of digested prey, before eventually being fed whole fish (3). Wedge-tailed shearwater chicks grow much larger than the adults during the nestling period, increasing to a weight of around 560 grams before dropping to around 430 grams. The chick remains in the burrow for the whole of the nestling period but is generally deserted by the adult wedge-tailed shearwaters a few weeks before fledging, which typically occurs after 103 to 115 days (2) (3).