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Tuatara: Volume 21, Issues 1 and 2 (New Zealand Albatrosses and Petrels: an Identification Guide)

Group 2— — The Large Procellaria Petrels — and Gadfly Petrels

Group 2—
The Large Procellaria Petrels
and Gadfly Petrels

(a) Procellaria Petrels
(Length 45-56 cm.)

Four species of these large, handsome petrels occur in New Zealand waters. Three are entirely black with contrasting pale or bi-coloured bill patterns, whereas the fourth is grey above and white below with dark underwings.

The endemic Westland Black Petrel (13), (see Fig. 10), and Black Petrel (14) are essentially subtropical in distribution, the latter species migrating to the North Pacific for the winter. More southern in range is the White-chinned Petrel (12) which, together with the Grey Petrel (23), is commonly encountered in subantarctic waters.

The above petrels are usually seen at sea as solitary birds or small groups of a dozen or so individuals. They are powerful fliers and skilled at gliding with stiffly outstretched wings for hours on end. At night they feed on squid, crustaceans and fish.

(b) The Gadfly or Pterodroma Petrels (Length 28-43 cm.)

The gadfly petrels are so named because of their swift dashing flight, which some observers have likened to that of bats. Twenty ‘species’ of gadfly petrels representing the genus Pterodroma (Greek: pteron = wing; dromos = running: hence ‘wing-runner’) are covered in this guide. They are an interesting and diverse group, with a great range of plumage colouration, size and breeding behaviour. Most are greyish-black above and white below, with mottled grey and white foreheads and short, chunky, black bills. The gadfly petrels are more robust in over-all appearance than are the slender-bodied shearwaters (see below) and have slightly broader wings which are not as attenuated at the tips as most of the shearwaters. The neck is short and thickset, while their tails are fairly broad. A dark eye patch is another common feature, as are the mostly black wings. The latter frequently have a discernible open ‘M’ marking formed by the black primaries and some of the upper- page 28 wing coverts. Completely dark species and phases of species occur, making problems of identification particularly challenging.

A group comprising the smallest of the gadfly petrels are generally referred to as the ‘Cookilarias’. Because they are all so very similar to each other in size, colour and flight behaviour, specific identification is often difficult at sea. The conspicuous underwing pattern of some species, however, is a useful aid to their identification. The term Cookilaria is derived from the Cook's Petrel (34) which was the first of these birds to be described and whose name honours the navigator, Captain James Cook.

The gadfly petrels are generally solitary at sea and feed on squid and crustaceans, mainly taken at night.

Whereas many of the above birds frequent subtropical or tropical seas, the Blue Petrel is a bird of colder waters. It is unique among petrels in having a white-tipped tail combined with bluish-grey upperparts and white underparts. For this reason, it is placed in a genus of its own. Great flocks of this interesting species can be observed in Antarctic waters.

(c) Prions
(Length 25-31 cm.)

Prions are small, bluish-grey petrels with white underparts. Six species occur in New Zealand waters; four breed in the region, the other two being regular winter visitors from the Indian Ocean. In addition to their blue upperparts, they are distinguished by their black-tipped tails and conspicuous black open ‘M’ marking stretching over the wings. The bill can be broad and massive as shown in the Broad-billed Prion (42) or short and slender as that of the Thin-billed Prion (45), but distinguishing prion species at sea comes only with practice. The Fairy Prion (44) and the Broad-billed Prion (42) are the most abundant prions north of the Subtropical Convergence (i.e. north of Foveaux Strait). Further south, in subantarctic and colder waters, the Antarctic Prion (43) predominates. Prions are gregarious at sea, sometimes gathering into flocks of several thousand birds when their impetuous and twisting flight gives them the appearance of countless snowflakes. They feed from the surface of the sea, mainly on crustaceans.