WILSON'S STORMY PETREL. 553 



DESCRIPTION. 



The plumage generally is sooty-brown, darker on the crown ; primaries and tail 

 brownish-black; wing coverts and inner secondaries ashy-gray; rump, feathers of 

 the sides adjoining it, and outer lower tail coverts, white ; bill black ; iris dark-brown ; 

 tarsi and feet black. 



The female differs only in being rather smaller. 



This is larger than Wilson's Petrel, and has a much stronger bill : it may be 

 readily known from it by its forked tail, and the interdigital webs being entirely 

 black. 



Length, eight inches; wing, six and a half; tail, three; bill, two-thirds of an 

 inch ; tarsus, one inch. 



rilHIS species is the most abundant of our Petrels. It is, 

 JL in fact, the only one that breeds here ; and all others 

 may be regarded as wanderers. About the first week in 

 June, in the latitude of the islands on the north-eastern coast 

 of Maine, it pairs. Breeding in communities, it soon begins 

 its nest. This is composed of weeds, short grasses, and 

 small pebbles, which are arranged in a flat structure, at the 

 end of a burrow constructed by the birds, or in the fissures 

 and crevices of rocks on the islands off our northern coast. 

 In this a single egg is deposited, which is of a pure-white 

 color, with an obscure lilac ring around one end, consisting 

 of fine confluent dots. It is nearly oval in form, and 

 averages in dimensions about 1.30 inch in length and .96 

 inch in breadth. A large number of specimens in my col- 

 lection exhibit a variation of from 1.35 to 1.24 inch in 

 length, and from 1 inch to .80 inch in breadth. These eggs 

 soon become discolored and dirty, from the nature of the 

 nest and the habits of the bird ; but originally they are pure- 

 white. Their shell is exceedingly fragile, and a little rough 

 to the touch, like that of the eggs of all birds of this class. 



THALASSIDBOMA WILSONII. Bonaparte. 

 Wilson's Stormy Petrel. 



Procellana pelagica, Wilson. Am. Orn., VII. (1808) 90. 



Thalassidroma Wilsonii, Bonaparte. Syn. (1828), No. 308. Nutt. Man., II. 

 (1834) 324. Aud. Orn. Biog., III. (1835) 486 ; V. (1839) 645. /&., Birds Am., VII. 

 (1844) 223. 



Oceanites Wilsonii, Bonaparte. Cons. Av. II. (1855) 199. 



