The fluttering shearwater, with its distinctive, ‘flutter-glide’ flight, is a ubiquitous seabird of inshore waters in the top half of New Zealand, especially in the northern-eastern North Island and Marlborough Sounds-Cook Strait regions. It is often seen in flocks, sometimes numbering thousands of birds, moving rapidly while foraging. Fluttering shearwaters feeds in association with schools of fish (e.g. kahawai, trevally) or in massive groups at the surface on crustaceans; and at times, resting in large, dense rafts. During the post-breeding period, a considerable proportion of the population remain within local waters, where fluttering shearwaters are a common sight inshore throughout winter months. They have been observed visiting colonies during the non-breeding period. However, they are also trans-Tasman migrants and are recorded in considerable numbers in eastern and south-eastern Australian waters from February to August. These birds may all be pre-breeders, and have included band recoveries of recently-fledged chicks.

Identification

The fluttering shearwater is a small dark-brown-and-white shearwater. A dark cap extends below the eye in a smudgy line to a partial collar, giving the head a dusky appearance. The upper-surfaces are uniformly dark grey-brown, including neck, wings and tail. Distinctive white patches (‘saddle bags’) extend up from the white flanks, behind the wings to form white sides to the rump. White extends from the chin to the under-tail, apart from a dark thigh patch. The under-wings have a dusky appearance with variable dark markings on the inner-wing, although in strong low light can appear white. The appearance can vary markedly with light conditions. The bill is long, thin, and dark; the legs and feet are pinkish-brown with dark webs. The feet extend beyond the tail in flight. They moult from late January, appearing ragged, with the dark upper surfaces faded to mid-brown. Their flight is best described as ‘determined’, i.e. low and fast, with bursts of rapid wing-beating (fluttering) interspersed with short glides.

Voice: a distinctive, staccato ka-hek-ka-hek-ka-hek, mostly made in flight, over and around colonies, however very occasionally heard calling at sea amongst feeding flocks.

Similar species: Hutton’s shearwater is a very similar-looking, but larger bird. Confusion with Hutton’s shearwater is most likely in central New Zealand around Cook Strait where both species overlap during breeding; Hutton’s shearwater is a rare visitor to northern New Zealand waters and mostly likely before or after breeding. Its head is darker, with little white showing on the chin and throat; the under-wing pattern is also darker. In the hand, Hutton’s shearwater has a longer, slimmer bill, and dark outer vanes to the undertail coverts (these are white in fluttering shearwaters). Little shearwater occurs with fluttering shearwater in northern New Zealand waters. Little shearwater is smaller and has white extending above the eye. Combined with the shorter bill and white underwings, it has a ‘cleaner’, sharper appearance than fluttering shearwater. Subantarctic little shearwater (southern New Zealand) is smaller, darker above and whiter below (especially underwings). Manx shearwater and Newell’s shearwater are both very rare vagrants to New Zealand; both are bolder black-and-white than fluttering shearwater, with a triangle of white reaching up to the ear, more prominent white ‘saddle-bags’ and cleaner white underwing with broad dark trailing edge (the two differ from each other in mainly in the colour of their undertail).