THE COMMON STOEM PETREL. 427 



THE COMMON STORM PETREL (Tlialassidroma pelagica). 



This species is the true " Mother Carey's chicken " of the 

 sailors, and also the " witch," the " spency," the " storm 

 finch," and a variety of other names, the abundance of which 

 shows, that it is at once a bird of common occurrence and of 

 some interest. 



During its pelagic period, it is seen on most part of the 

 seas, especially those on the north, west, and south-west of 

 Britain, where it is the last bird to leave the outward-bound 

 ship, and the first to meet ships returning home. It plays 

 about the vessels, and outstrips their swiftest course, skim- 

 ming the surface of the water with equal ease and grace, and 

 tipping so regularly both with wings and feet, that it appears 

 as if running upon all fours. The wings do not, however, 

 get wet or splash, and the bird can make wing in any direc- 

 tion of a moderate wind, apparently with very little fatigue. 

 No part of the weight appears to be borne on the feet, while 

 the bird is in progress forward. When the wings are raised, 

 the weight is borne on the breast, supported by the repulsion 

 of the water to the oily feathers ; and the feet are drawn for- 

 ward while the wings are descending, and give their impul- 

 sive stroke forward while the wings are rising, the two actions 

 combining so well as to produce, not jerks, but a uniform 

 skimming motion. They often alight on ships, and make 

 them slippery with oil. Though it cannot, for the reasons 

 that have been stated, feed so well in the troubled sea as 

 when the water is smooth, it can keep its way, even though 

 the waves run high, and it appears to skim along close on the 

 surface, adapting its path to the flexures of the waves. In 

 strong winds, however, both the speed and the undulations 

 of the course, upward and downward, are in so far optical 

 deceptions. In those cases, the motion of the bird is to 



