PETRELS. 91 



TUBE-NOSED SWIMMERS. (ORDER TUBINARES.) 



PETRELS. (FAMILY PROCELLARIID^E.) 



Petrels, or " Mother Carey's Chickens," are true chil- 

 dren of the sea. Their home is the ocean, and they come 

 to land only when nesting. To the 

 PiatTiv landsman, therefore, they are strangers, 



but to most people who have been to 

 sea they are known as the little, white-rumped swallow- 

 like birds who on tireless wing follow in the wake of the 

 ship day after day, patiently waiting for the food which 

 experience tells them will be thrown overboard. 



Two species of Petrels are found off our coasts, Wil- 

 son's and Leach's. The former has a yellow area in the 

 webs of the toes and a square tail, while Leach's Petrel has 

 the webs of the toes wholly black and a slightly forked 

 tail. These differences, however, would not be appre- 

 ciable at a distance. Wilson's Petrel nests in certain 

 islands of the southern hemisphere in February, and 

 later migrates northward, reaching our latitude in May 

 and spending the summer, or what in fact is its winter, 

 in the North Atlantic. It is, therefore, probably the 

 Petrel most frequently seen by transatlantic voyagers at 

 this season. 



Leach's Petrel nests on our coasts from Maine north- 

 ward, arriving from the South in May. The nest is 

 made in a burrow in the ground or beneath a rock, and 

 a single white egg is laid. Generally one of the birds 

 spends the day on the nest while its mate is at sea, but 

 at night the incubating bird leaves the nest, its place being 

 taken probably by the one who has been feeding during 

 the day. 



