The Birds and Poets 49 



warm weather, but the Baltimore oriole, the 

 scarlet tanager, the bobolink, many of the war- 

 blers and other birds will not come until May. 

 They are true to May, no matter how warm a 

 welcome April may offer them. 



Contrary to the popular impression and the 

 early opinions of students of migration, tempera- 

 ture has but little influence upon the migratory 

 habits of the birds. Food supply is undoubtedly 

 the most controlling consideration. Those birds 

 whose favorite food can readily be obtained in 

 winter, uninterrupted by snow or other weather 

 conditions, are usually permanent residents, and 

 do not migrate southward in autumn. Birds have 

 wonderful breathing capacity, and hence great 

 animal heat, and seldom are seriously affected by 

 cold weather alone. Tiny chickadees, creepers 

 and nuthatches seem less inconvenienced by the 

 cold, sharp air of winter than we do. The food 

 of many birds is quite inaccessible in winter, how- 

 ever, and the ever-present and controlling impulse 

 of self-preservation unfailingly directs them to 

 their food supply. But, given an abundance of 

 its favorite food, a bird's movements no longer 

 seem to be governed by the calendar. Red-headed 

 woodpeckers, for example, were supposed to 

 migrate southward in the fall and pass the win- 

 ter south of Maryland, until Dr. Merriam, in 

 his interesting account* of the habits of this spe- 

 cies, tells that in one county in New York their 



•Bull. Nutt. Orn. Club, iii, 1878, pp. 123-128. 



