MONOGRAPH OF THE PETRELS. 



Scottish Antarctic Expedition, and it was doubtless P. assimilis which was observed 

 by Mr. M. J. Nicoll during the voyage of the "Valhalla" between St. Paul's Rocks 

 and Tristan da Cunha (Ibis, 1906, p. 674). It is said to occur on some of the North 

 Atlantic Islands, such as Deserta Grande, but I cannot but think that the bird 

 referred to is P. bailloni. 



Sir Walter Buller mentions that, in December, 1888, Mr. Reishek discovered adult 

 birds of P. assimilis on Chicken Island, occupying the same burrow as the Tuatara Lizard 

 (Sphenodon punctatum). They were plentiful on the south-eastern side of the 

 island, but less so on the smaller islands in the vicinity. During the breeding season, 

 which commences in October, the male habitually goes to sea during the day, 

 returning to the burrows at night, and its habits resemble those of other species of 

 Shearwaters. Like Majaqueus parkinsoni and (Estrelata coolci, P. assimilis goes 

 somewhat further inland to nest than P. gavia, usually selecting the woody parts of the 

 island and a high elevation, where it may be seen sitting on the trees in the moonlight 

 uttering its cry, " ha-kwa-kwa." 



The egg of this Shearwater is ovoido-conical in form, measuring 2.2 inches in 

 length, by 1.4 inch in breadth, and when fresh is perfectly white (Buller, Birds N. Zeal., 

 2nd ed., II., p. 237, 1888) ; those from Raoul Island and Auckland, N. Z., in the British 

 Museum measure : Axis, 1.95-2.0 inches ; diam., 1.4-1.45. 



Adult male. General colour above slaty-black, deeper black on the scapulars and 

 wing-coverts ; quills black, with a shade of slaty-grey extending over nearly the whole 

 of the outer web ; tail-feathers black ; head black, like the back ; upper part of 

 lores black, but the lower part sharply divided and white, like the sides of the 

 face and cheeks ; upper and lower eyelid white ; ear-coverts white, with a narrow line 

 of black along the upper margin, above which is a broad but ill-defined band of white, 

 extending from above the eye and mottled with black streaks ; entire under-surface 

 of body pure white, including the sides of the neck, which are separated from the black 

 upper-surface by some mottled feathers, which are white, with a sub-terminal black 

 spot or bar ; under tail-coverts pure white, with no dusky margins to the lateral 

 coverts ; under wing-coverts, axillaries and quill-lining all pure white, the quills being 

 ashy-brown below, with the inner webs of the primaries entirely white ; " bill dark 

 horn-colour ; tarsi and toes greenish yellow, webs yellowish orange " (J. Gould). 

 Total length about 10.5 inches ; culmen, 0.95 ; wing, 7.15 ; tail, 2.6 ; tarsus, 1.55 ; 

 middle toe and claw, 1.7. 



Adult female. Similar to the male. Total length about 10.5 inches ; culmen, 

 1.0 ; wing, 7.2 ; tail, 2.7 ; tarsus, 1.55 ; middle toe and claw, 1.7. 



The colours of the bill and feet have been given by other observers as follows : — 

 Hauraki Gulf (Buller) : — Bill bluish-black ; feet greenish-grey, with yellow 



interdigital webs, marked with black on the outer edge. 



Gough Island (Scotia Exped.) : — Basal half of bill blue, distal part and nasal 



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