NON-INDIGENOUS BRITISH BIRDS. 317 



at the foot of the cHffs, at a distance of several feet 

 from the open. The bird is a close sitter, and shuns 

 the light of day. 



Range of egg colouration and measurement : 

 Bulwer's Petrel only produces a single ^gg for a sitting. 

 This is pure white. Average measurement, 175 inch in 

 length, by r25 inch in breadth. Incubation is performed 

 by both sexes, but the duration of the period has not 

 been ascertained. 



Diagnostic characters : The size and absence of 

 spotting is sufficient to distinguish the Qgg of Bulwer's 

 Petrel from those of any other species breeding in the 

 same area. 



Family PROCELLARIID.-E. Genus Oceanites. 



WILSON' PETREL. 



Oceanites wilsoni {^Bonaparte). 



(British : Rare summer visitor during the period of the 

 Antipodean winter.) 



Single Brooded. Laying season, January and February 

 (Southern Hemisphere). 



Breeding area : Southern Seas. Wilson's Petrel is 

 only known to breed on Kerguelen Island, but probably 

 does so on the various isolated rocks and islands that 

 stud the Southern Ocean right round that portion of the 

 globe. 



Breeding habits : The only information respecting 

 the nidification of Wilson's Petrel is that obtained by 

 the Rev. A-. E. Eaton, the naturalist to the Transit of 

 Venus Expedition, on Kerguelen Island. This Petrel 

 is gregarious at its breeding grounds, and there can be 



