Allen on an Inadequate "Tlieory of Birds' Nests." 23 



more olive,' the upper parts brighter and more greenish ; rump and upper 

 tail-coverts plumbous-gray. From a specimen killed at Mt. Carmel, 111., 

 July 22, 1875 ; in my collection. In this specimen a large patch on each 

 side the breast is bright gamboge-yellow (as is also a row of ' pin-feath- 

 ers ' along the middle of the throat), indicating the adult plumage." — R. R. 



23. Helmitherus vermivorus. 



r " First plumage. Remiges, rectrices, primary coverts, and alulae aa in 

 the adult. Rest of the plumage, including the whole back, lesser, mid- 

 dle, and greater wing-coverts, buff, deeper below, more brownish on the 

 back and base of the wing-coverts. Pileum with two badly defined stripes 

 of grayish-brown, and a narrow streak of the same behind the eye. From 

 a specimen in Mr. Henshaw's collection obtained near Washington in July, 

 1876." — R. R. 



AN INADEQUATE "THEORY OF BIRDS' NESTS." 



By J. A. Allex. 



Why the thousands of species of birds build each a peculiar nest, 

 differing more or less in situation and architecture from those of all 

 other species, is a question which has as yet received no satisfactory 

 answer. As a rule, the nest, including its location, the materials 

 and manner of its construction, is as distinctive of the species as 

 the number, size, form, and color of the eggs, or, in some instances, 

 as any fact in its history, not excepting even the details of struc- 

 ture and coloration of the bird itself. Why this is so we can per- 

 haps explain when we can satisfactorily account for the diversity 

 of song that is scarcely less a specific characteristic. Yet the struc- 

 ture and position of the nest, even among birds of the same spe- 

 cies, is more or less varied by circumstances, sometimes even to a 

 striking degree. In some cases the influence of peculiar surround- 

 ings is most obvious, as when, for instance, a species that habitu- 

 ally nests in trees, like the Carolina Dove, is found in treeless 

 regions to place its nest on the ground, or when a Woodpecker, 

 under similar circumstances, excavates for its nesting-site a cavity 

 in a clay-bank. Not unfrequently birds exhibit in their choice of 

 nesting-sites something quite akin to intelligent foresight, as is 

 manifestly the case when such species as the Brown Thrush and 



