448 THALASSIDROMA. STORM-PETREL. 



able to fly. The sitting birds are easily caught in their nests, 

 as they seldom attempt to fly off". On being seized, these 

 birds, like the Fulmars, discharge the contents of their sto- 

 machs, generally consisting of oil. They feed on oily and 

 fatty substances, small Crustacea and mollusca, which they 

 pick up as they skim over the waters. They float lightly, 

 like Gulls, but are incapable of diving. Their flight is buoy- 

 ant and rapid, somewhat resembling that of swallows. The 

 species, which are not numerous, are distinguished chiefly by 

 their relative size, and the form of the tail. One, Thalassi- 

 droma pelagica, is common in the British seas, and breeds in 

 our northern islands ; another, Thalassidroma Leachii, al- 

 though uncommon, breeds in St. Kilda. Some individuals 

 only of other two species have been met with in Britain. 



These birds are confounded by navigators under the 

 general name of Mother Carey's Chickens, so that the limits 

 of the distribution of the species are not well known. They 

 are held in abhorrence by sailors, being supposed to prog- 

 nosticate stormy weather, especially when they fly around, or 

 in the wake of the ship. The circumstances under which 

 they approach vessels have not, however, been correctly de- 

 scribed. Some say they come up before a gale for shelter, being 

 able, by their rapid flight, to outstrip it ; while others allege 

 that in rough or calm weather, before a gale or before a calm 

 alike, they make their appearance, and that their purpose is 

 simply to pick up the objects of food raised by the agitation 

 of the water, or such as are thrown overboard. 



