Berta zampone

Identificazione

This is a medium to small-sized shearwater with a dark-brown-and-white body. The upper parts, including neck, wings and tail, are uniformly dark brown. The face and neck have a grey-brown colour gradually fading into white below the eye. The under body, from chin to the under-tail, is white except for a dark thigh patch that can be seen in flight. The bottom wing is commonly white while the axillary area is covered in grey-brown fur. Under light conditions, the appearance is different. The fluttering shearwater has pinkish-brown legs and feet with dark webs, and the feet extend beyond the tail in flight. The bill is long and thin with dark colour. The tail is fan-shaped and short in flight and it has mixed colours – dark brown and white.<p>Moulting starts from late January and the dark upper surfaces fade to mid-brown quickly. The colour of birds close to moulting (February to April) is pale rusty brown and they appear ragged at this stage. Their voice is unusual and disjointed: ka-hek-ka-hek-ka-hek and usually made in flight. Their flight pattern is somewhat determined, low and fast. Rapid spurts of wing-beating interspersed by gliding.<p>The average body mass of females is 302 g while males is 243 g. Their eggs are pure white and oval. The young birds have the same colour as adult from the nest, but with lighter color in the margin of wing-coverts. Nestlings have very thick slate-coloured soft feathers on the upper and white down on the under.

Tassonomia

Nome scientifico

Puffinus gavia

Autorità

(Forster, JR, 1844)

Ordine

Procellariformi

Famiglia

Procellaridi

Genere

Puffinus

Areale e habitat

Fluttering shearwaters are an endemic species to New Zealand, where they breed throughout the warmer months of the year, from September to February. However, during the non-breeding months of the year, between March and August, vast numbers are seen throughout eastern and south–eastern Australia, though most seem to linger close to the breeding colonies. It is suspected that it is the juveniles that migrate, whereas the adults stay confined to the rich waters of New Zealand; however, this is not fully understood.<p>Fluttering shearwaters breed on coastal islands throughout New Zealand, with large populations on islands throughout the north-east North Island, such as the Aldermen Islands, Moturoa Island, Bream Islands, north-west Chicken islands, Mercury Islands, Motuharakeke Island (Cavalli Islands), as well as islands throughout the Marlborough Sound/Cook Strait region of the South Island, with a majority of these offshore islands within 40 km of the mainland.<p>The habitats of fluttering shearwater are marine and terrestrial, including coastal and marine areas, scrubland and forest. They are most commonly found in subtropical waters and warm water (24 °C) of intermediate to high salinity (35%). The birds are common on inshore areas that are easy to enter such as harbours, inlets, bays and straits. They usually select stony, scrub-covered slopes near the peak, as well as cracks and holes in the rock far from the water to breed, which is a benefit for taking off.

Areale riproduttivo

PO : islets of ne North I. and Marlborough Sounds (ne South I.; New Zealand)

Areale non riproduttivo

to s, e Australian waters

Migrazione

Complete migrants

Comportamento

Fluttering shearwaters have a habit of fluttering their wings quickly and beat the feet when they fly away from the sea. A large group of fluttering shearwaters gather together and sit on the water in rafts through the months of mid-December, January and February. Sometimes, rafts will form just near the coastline.

Conservazione

Tendenza della popolazione

declining