COMMON STORM-PETREL. 463 



the feathers are put aside. The axillar feathers, and some of 

 the lower -wing-coverts, are white toward the end. 



Length to end of tail 5{% inches ; extent of wings 13|; 

 bill along the ridge -^, along the edge of lower mandible -^ ; 

 wing from flexure 4-Lfi- ; tail 2^-^ ; tarsus -fi- ; hind toe and 

 claw Jj ; second toe -^, its claw -^ ; third toe -j^, its claw 

 -fg- ; fourth toe -^, its claw ■^. 



Female. — The female is similar to the male, but some- 

 what smaller. 



Length to end of tail 5-^ ; extent of wings 13^. 



Variations. — Adult birds, having the plumage fresh, differ 

 very little in colour. In that state they have the upper parts 

 of a glossy greyish-black, the secondary qviills distinctly edged 

 with white toward the end, the lower tail-coverts about a 

 fourth of an inch shorter than the middle tail-feathers, which 

 exceed the lateral by about half an inch. But in summer? 

 when the feathers have been worn, the tail is often almost or 

 entirely even, the lower coverts of the same length ; the 

 secondary quills have no white, and they, as well as the 

 wing-coverts, have assumed a brownish colour. The white 

 feathers of the rump have the shafts generally, but not always 

 black. Considerable differences are observed in size. Thus, 

 in four specimens before me, the wing is 4\^, 4^, 4-L^, 5^^- 

 long ; the tarsus if, \^, \^, -^ ; the middle toe and claw 

 if, If, i^, if. It appears that, like the Skua, it sometimes 

 has a few white feathers ; at least, an individual caught off 

 the Isle of May, in June, 1832, had four on the breast; and 

 another from Shetland, in my collection, has one on the nape. 



Habits. — The Petrels have received their name for a 

 habit, common to them and the smaller Gulls, of letting their 

 legs hang down, and patting the water with their feet, when 

 hovering over it for the purpose of picking up some article of 

 food. On such occasions they seem to walk upon the sea, 

 although, in fact, entirely sustained by their outspread wings 

 and on this account they have been likened to the Apostle 

 Peter, whose miraculous, though, through want of faith, only 



