194 BIRD STUDIES WITH A CAMERA 



questions of food and climate must be considered, 

 we have here the problem reduced to its simplest 

 terms; and in the desire for seclusion during the 

 breeding season which induces birds to conceal their 

 nests, if possible perhaps near by, but if necessary 

 after a journey of varying length undertaken espe- 

 cially for the purpose, we have a good and sufficient 

 cause for the origin of bird migration. 



An attempt to explain the present manifestation 

 of the migratory movement involves a studj^ of the 

 climatic changes to which our globe has been sub- 

 jected. No doubt many birds controlled by "he- 

 redity of habit" make semiannual journeys which 

 at one time were necessary, but under existing cir- 

 cumstances are no longer required. Why, for ex- 

 ample, should the Bobolink winter south of the 

 Amazon, while its ally, the Red-winged Blackbird 

 {Agelaius phceniceus) , does not leave the eastern 

 United States ? I have, however, no intention of 

 writing an essay on bird migration, and these 

 thoughts are presented merely as preliminary to a 

 study of the life of Pelican Island, of a visit to 

 which they are in part the outcome. 



Pelican Island is situated midway between the 

 northern and southern extremities of Indian River, 

 near the eastern shore of a key which here makes 

 the river about three miles wide. It is triangular 

 in shape and contains about three acres of ground, 

 on which grow a few black mangroves, a cabbage 

 palm or two, and great patches of grass; but at 

 least one foiirth of its surface is bare ground. 



On one of the islands of the near-by Narrows a 

 few pairs of Brown Pelicans are said to have nested, 



