Christmas Shearwater

The Christmas shearwater, known in its native tongue as ʻaoʻū, is a medium-sized member of the shearwater family, boasting a slender body approximately 36 cm in length. With a wingspan nearing 75 cm and a weight around 350 grams, this bird is cloaked in a dark plumage, predominantly blackish-grey with a hint of rusty-brown. The underside is slightly paler, and a delicate fringe of white can be seen under the chin, with pale edges to the upperwing coverts. Its feet are a brown-grey, and it possesses a dark bill and eyes. Both male and female are similar in appearance, as are the fledglings. The nestlings are adorned in dark grey down.

Identification Tips

Distinguishing the Christmas shearwater from its relatives can be a subtle art. It bears a resemblance to the sooty and short-tailed shearwaters but is set apart by its dark brown underwings and more diminutive size. Its tail, not blunt unless spread, tapers to a point in flight, accentuated by feet that extend beyond the tail-tip. Its flight is often leisurely, akin to that of petrels, which may lead to confusion with the rare Fiji petrel. However, the Christmas shearwater's bulbous head and thin long bill, characteristic of shearwaters, differentiate it from the slim-headed, thick-billed Fiji petrel.

Habitat

The Christmas shearwater is a creature of sandy islands, seeking refuge under dense vegetation or rock outcroppings to nest.

Distribution

This bird's breeding grounds are scattered across the Central Pacific's remote islands, including the Northwestern Hawaiian Islands, Tuamotu, the Marshall Islands, Kiritimati, and Sala-y-Gómez. It has vanished from some islands, such as Wake Island. Its non-breeding range spans the Pacific, with sightings off the coasts of Mexico, Guatemala, and as far as the Bonin Islands, though it is a rare visitor to the south, with only a couple of records off Fiji.

Behaviour

The Christmas shearwater is a highly pelagic bird, relying on predatory fish like tuna to drive its prey to the surface. It exhibits both the dynamic soaring flight typical of shearwaters and the more leisurely wingbeats of its petrel relatives.

Diet and Feeding

At sea, the Christmas shearwater indulges in a diet primarily composed of squid and fish, including flying fish and goatfish. Its feeding strategy is opportunistic, taking advantage of the chaos created by larger predatory fish.

Breeding

Breeding sites are chosen for their cover, with the bird nesting on the surface or under dense vegetation or rocks. It lays a single white egg, with the timing of laying and the period to fledge varying across different islands.

Conservation status

The Christmas shearwater is currently classified as Least Concern by the IUCN. However, like many seabirds, it faces threats from fishing, plastic ingestion, and habitat degradation. On Laysan Island, for instance, introduced rabbits and rats have posed significant challenges to the species' survival. Despite these threats, the bird's wide range and considerable numbers have not yet tipped it into a more precarious conservation status.