Vol. XVIII 

 I go I 



1 Bishop, Winter Birds of Pea Island, N. C. 263 



Boreal forms, of which Otocoris, Cakarius and Acanthis are good 

 examples, forced south in winter by lack of food, seem to move 

 in regular order, keeping individually about the same north and 

 south relations to the bulk of the species, or wander in large flocks 

 in search of food, as Ampelis, Loxia and Pinicola. 



In the other class will be found species developed either in the 

 Austral Zone of North America or the American Tropics, which, 

 originally forced north in summer for reproduction by the crowd- 

 ing of life in the tropics, repeat this movement yearly through the 

 continued operation of the primary cause and the formation also 

 of habit. In these birds it appears that those breeding farthest 

 north, though appearing at midway stations in the fall after the 

 birds of the same species breeding there have left, pass as far 

 or farther south in winter. Birds of the genera Hesperocichla^ 

 Hylocichla^ Junco^ Leiicosticte, Zonotrichia, Melospiza^ Passerculus, 

 Ammodratnus, Dendroica and Vireo will illustrate this. In the 

 spring these northernmost breeding birds seem to pass the half- 

 way stations, as a rule, when the birds breeding there are already 

 at home. This movement I think I have noticed in species of the 

 genera Qiiiscalus^ Agelaiiis, Icterus, Melospiza^ and Ammodramus . 

 On the basis of this Dr. Coues separated Dendroica ccerulescejis 

 cairnsi before he had seen a bird from the summer habitat of this 

 subspecies. 



Austral birds as a class would then pass north in summer chiefly 

 because their winter homes and the intermediate stations are 

 already occupied, and return in winter toward the original habitat 

 of the species. Boreal birds on the other hand, forced south 

 originally and each year by the lack of food in their homes in win- 

 ter, would return north when approaching summer makes it possi- 

 ble, and in strong-flying species might readily develop the habit of 

 long journeys, as is shown by the boreal Limicola;. 



I do not wish to claim that these rules will hold with all species ; 

 I offer them simply as a contribution to the study of migration. 



I. Gavia imber. Loon. — A \oung female, in which the first nuptial 

 plumage is appearing on the back, wing-coverts, rump and tail-coverts, 

 was taken on February 15. The feathers of the head and neck still 

 show the downy texture and the black tipping on the side of the throat 

 characteristic of the first winter plumage. 



