68 THE MIGRATIONS OF BIRDS 



said to leave England several weeks before the 

 young essay migratory flight. The young cowbird 

 of the United States, reared by a foster-parent, 

 flocks with other young of its kind when grown, and 

 in many instances can hardly have adult guidance 

 in migration. Nor can we fall back upon guidance 

 through leadership of experienced birds of other 

 species, since all birds do not follow the same route. 

 It is difficult to explain under the guise of leadership 

 the diff'erence in line of flight between the Baird's 

 sparrow, which passes to the southwest from the 

 prairies of Dakota, and the Leconte's and Nelson's 

 sparrows, which fly directly south or southeast from 

 the same point. Under these circumstances one 

 must think that under leadership of other forms 

 there would be constant sad confusion among young 

 birds, which does not happen. 



The movements of many seabirds are still more in 

 point. Two species of albatross, the wedge-tailed 

 shearwater, and the white-breasted petrel, nest on 

 certain islands in the Hawaiian Bird Reservation. 

 During part of the year these birds travel to distant 

 points on the open sea, yet return to the same low 

 sand islands each year to nest. The reflection of the 

 green water inside the coral reefs, thrown on the sky, 

 perceptible to those accustomed to it when the 

 atolls are below the line of vision, might explain the 

 return to islands within 20 or 30 miles, but will not 



