AN EXPEDITION TO THE SALVAGE ISLANDS. 413 



to be seen all about tbe burrows, and the marks of their teeth on 

 the empty shells were unmistakable. The birds, some of which 

 were quite freshly killed and almost untouched, were invariably 

 done to death by being bitten at the nape of the neck, and in 

 some cases part of the brain had been eaten. It seemed curious 

 that these comparatively small Mice should be able to kill a bird 

 several times larger than themselves, and provided with a fairly 

 strong hooked bill ; but no doubt the Petrels get caught in the 

 end of their burrow, and being terrified, do not even try to defend 

 themselves. We obtained no young of this species, and the most 

 advanced eggs were at most but half incubated on April 27th. 

 Almost more interesting than the White-breasted Petrels was the 

 square-tailed, white-rumped Petrel (Oceanodroma cryptoleucura), 

 of which we obtained but a single example, caught at night with 

 a lantern at Great Salvage, though we saw several flying over 

 the neighbouring seas from the deck of the ' Pedro.' This bird 

 had not yet come to shore to breed, and the only egg we obtained 

 was taken at Porto Santo, near Madeira, in the month of June. 

 It had always been previously supposed that the only small white- 

 rumped Petrel met with in these seas was Leach's Fork-tailed 

 Petrel (0. leucorrhoa). That this bird also occurs there is 

 certain, for we have seen a specimen obtained at the Canaries by 

 Mr. Meade-Waldo, but it appears to be merely a straggler so far 

 south ; and certainly the square-tailed species is the bird that has 

 generally been mistaken for it. 0. cryptoleucura was described a 

 few years ago from the Sandwich Islands, and no one had any 

 idea that it was also found in the Canary seas, so that this 

 discovery is a matter of considerable interest to ornithologists. 

 The birds obtained at St. Helena also belong to this form, and 

 not to Leach's Petrel, as has been generally believed. It may be 

 useful to state the main differences between the two. 



0. leucorrhoa has the tail deeply forked, the outer feathers 

 being much longer than the middle pair, and dark to the base; 

 while the upper tail coverts are uniform white, not tipped with 

 black. 



0. cryptoleucura has the tail nearly square, the outer feathers 

 being only slightly longer than the middle pair, the basal part of 

 the outer feathers is white, and the upper tail coverts are white, 

 tipped with black. 



The only other Petrel met with was the brownish- black 



