WILSON'S PETREL. 451 



some cases the holes appeared to be frequented for a month or more before 

 the eggs were laid. 



The eggs of Wilson's Petrel are white, with a more or less obscure zone 

 of minute reddish-brown spots generally round the large end. They are 

 about the same size as those of the Fork-tailed Petrel, and consequently 

 cannot be distinguished from them, averaging about 1/3 inch in length and 

 9 inch in breadth. The food of Wilson's Petrel is not known to differ 

 from that of the allied species. Of the migrations of this bird, and of 

 the habits of the young when they can fly, nothing appears to have been 

 recorded. 



It is not known that there is any difference in colour between the sexes 

 of this species. The adult, after the autumn moult, has the general colour 

 of the plumage sooty black, palest on the head and neck, and darkest on 

 the wings and tail ; the greater wing-coverts have pale grey margins, the 

 rump and upper tail-coverts are pure white, and the outermost under tail- 

 coverts are slightly marked with white. Bill black ; legs and feet black, 

 with the centre of the webs yellow ; irides dark hazel. It is not known 

 that immature birds differ from adults in colour. Young in down are 

 uniform brownish grey. 



Three other species of this family have been included in the British list. 

 A solitary example of the Capped Petrel (CEstrelata hasitata) was caught 

 on a heath near Swaffham, in Norfolk, in the spring of 1850 (Newton, 

 ' Zoologist/ 1852, p. 3691). It is doubtful whether a second example has 

 ever occurred in Europe, though it has been said to have occurred in France, 

 and nothing is known of its breeding-haunts. It has occurred in the West 

 Indies and probably breeds there. 



A solitary example of the Cape Petrel, or Cape Pigeon (Daption capensis], 

 is said to have been shot near Dublin on the 30th of October, 1881 (More, 

 'Ibis/ 1882, p. 346). This species is the most common Petrel in the Cape 

 seas, its range extending eastwards to Tasmania, and westwards almost to 

 Cape Horn. It is said to breed on the island of South Georgia, and 

 to have occurred on the French coasts; but its egg appears to be unde- 

 scribed. 



A single example of Bulwer's Petrel (Bulweria columbina) was found 

 dead on the banks of the Ure, near Tanfield in Yorkshire, on the 8th of 

 May, 1837 (Gould, ' Birds of Europe/ part 22) . It appears to be an inha- 

 bitant of the Atlantic Ocean, chiefly in the neighbourhood of Madeira and 

 the Canaries. It breeds on the Deserta Islands, near Madeira, in a similar 

 manner to other Petrels. Its egg is figured on Plate 56. As none of 

 these three species of Petrel have occurred on the island of Heligoland, 

 and only claim to be British birds in virtue of a single occurrence, which 

 may or may not have been a voluntary visit to our islands, it has not been 

 thought necessary to honour them with a special article. 



