Berta di Buller

Identificazione

Adults birds are 46–47 cm (18–19 in) in length, with a 97–99 cm (38–39 in) wingspan, and have been recorded to weigh 342–425 g (12.1–15.0 oz). The upperside of Buller's shearwater is bluish grey. A blackish stripe runs from the tertiary remiges to the primary wing coverts. The primary remiges are blackish, also; the two black areas do not meet at the hand, however; the area between them is a rather light grey, and under bright light may appear almost white. With the bird facing upwards, the pattern gives the impression of a broken black "M", with light grey interspersing areas.<p>The underside is bright white; on the head the upperside's grey extends town to eye height and the white cheeks may shine up conspicuously, as in the smaller shearwaters of Puffinus sensu stricto. The rectrices are blackish and the tail is wedge-shaped; the bill and irises are dark. Fledged juveniles already have the adult's colouration; the nestlings are covered in grey down feathers.<p>Compared to other shearwaters, the species is unusually easy to identify at sea by its combination of considerable size and the distinctive, M-shaped banding pattern on its upperside while flying, uniquely among its genus and more akin to some gadfly petrels (Pterodroma), the prions (Pachyptila) and their relative, the blue petrel (Halobaena caerulea). These are all much smaller birds, perhaps two-thirds in length and wingspan and less than half in bulk of Buller's shearwater.

Tassonomia

Nome scientifico

Ardenna bulleri

Autorità

(Salvin, 1888)

Ordine

Procellariformi

Famiglia

Procellaridi

Genere

Ardenna

Areale e habitat

Areale riproduttivo

PO : Poor Knights Is. (off ne North I., New Zealand)

Areale non riproduttivo

to subarctic north Pacific, also e Australia and w South American waters to c Chile

Migrazione

Complete migrants

Conservazione

Tendenza della popolazione

stable