xlii INTRODUCTION. 



cellular matter, and at no season of the year are the true birds 

 of passage so fat as at the approach of their migration. The 

 Gulls, Cranes, and Herons, almost proverbially macilent, are at 

 this season loaded with this reservoir of nutriment, which is 

 intended to administer to their support through their arduous 

 and hazardous voyage. With this natural provision, dormant 

 animals also commence their long and dreary sleep through 

 the winter, — a nutritious resource no less necessary in birds 

 while engaged in fulfilling the powerful and waking reveries of 

 instinct. 



But if the act of migration surprise us when performed by 

 birds of active power of wing, it is still more remarkable when 

 undertaken by those of short and laborious flight, like the 

 Coots and Rails, who, in fact, perform a part of their route on 

 foot. The Great Penguin (^A/ca impenms), the Guillemot, and 

 the Divers, even make their voyage chiefly by dint of swim- 

 ming. The young Loons ( Colymbus glacialis) , bred in inland 

 ponds, though proverbially lame (and hence the name of Lom, 

 or Loon), without recourse to their wings, which are at this 

 time inefficient, continue their route from pond to pond, 

 floundering over the intervening land by night, until at length 

 they gain some creek of the sea, and finally complete their 

 necessary migration by water. 



Birds of passage, both in the old and new continents, are 

 observed generally to migrate southwest in autumn, and to 

 pass to the northeast in spring. Parry, however, it seems, ob- 

 served the birds of Greenland proceed to the southeast. This 

 apparent aberration from the usual course may be accounted 

 for by considering the habits of these aquatic birds. Intent on 

 food and shelter, a part, bending their course over the cold 

 regions of Norway and Russia, seek the shores of Europe ; 

 while another division, equally considerable, proceeding south- 

 west, spread themselves over the interior of the United States 

 and the coast and kingdom of Mexico. 



This propensity to change their climate, induced by what- 

 ever cause, is not confined to the birds of temperate regions ; 

 it likewise exists among many of those who inhabit the tropics. 



