Berta minore

Identificazione

This shearwater has the typically "shearing" flight of the genus, dipping from side to side on stiff wings with few beats, the wingtips almost touching the water, though in light winds it has a more flapping flight than that of its larger relatives. In flight it looks cross-shaped, with its wings held at right angles to the body, its colouration changing from black to white as the black upperparts and white underparts are alternately exposed as it travels low over the sea.<p>At 25–30 cm (9.8–11.8 in) in length with a 58–67 cm (23–26 in) wingspan, it is like a small Manx shearwater but has proportionally shorter and broader wings, with a pale area on the inner flight feathers. Its bill is more slender than that of Manx, and its dark eye stands out against the surrounding white area.

Tassonomia

mtDNA cytochrome b sequence data indicate that the former North Atlantic little shearwater group (Boyd's shearwater, P. boydi and Barolo shearwater, P. baroli) is closer to Audubon's shearwater (Austin 1996, Heidrich et al. 1998), (although many taxonomists now consider them to be distinct species), and Rapa shearwater (P. myrtae), being closer to the Newell's and possibly Townsend's shearwater (Austin et al. 2004). Heinroth's shearwater was also sometimes considered a subspecies of this bird; the relationship between the little and Audubon's shearwater is probably not as close as long believed (Austin 1996, Heidrich et al. 1998, Austin et al. 2001, but see also Penhallurick &amp; Wink 2004, and Rheindt &amp; Austin 2005). The subantarctic shearwater was also considered conspecific (Onley &amp; Scofield 2007, Gill et al. 2010)

Nome scientifico

Puffinus assimilis

Autorità

Gould, 1838

Ordine

Procellariformi

Famiglia

Procellaridi

Genere

Puffinus

Areale e habitat

It breeds in colonies on islands and coastal cliffs, nesting in burrows which are only visited at night to avoid predation by large gulls.

Migrazione

Complete migrants

Comportamento

This is a gregarious species, which can be seen in large numbers from boats or headlands, especially on migration in autumn. It feeds on fish and molluscs. It does not follow boats. It is silent at sea, but at night the breeding colonies are alive with raucous cackling calls.<p>It nests in cavities located in grassy fields or in those found among rocks.<p>The little shearwater usually produces a clutch of one clear white egg, measuring around 51 by 35 millimetres (2.0 by 1.4 in). The egg is incubated for 52 to 58 days by both sexes.

Conservazione

Tendenza della popolazione

declining