28 Allen on an Inadequate "Theory of Birch' Nests." 



color among our native birds being rarely greater than in these 

 species. The subpensile nests of some of the Vireos are to be per- 

 haps more properly referred to the type of open nests. In either 

 case we find only slight sexual difference in color, with the olivaceous 

 hue of the back well fitted for concealing the female bird. But this 

 is in part offset by the usually light color and somewhat exposed 

 situation of the nest. 



4. The great bulk of the species fall of course into the fourth 

 category, or those with the nest open. These embrace (with two 

 exceptions, the Woodpeckers and the Kingfishers) birds of every 

 family represented in our fauna, and are about equally divided be- 

 tween ground-builders and those which nest in bushes or trees. As 

 a rule (as, in fact, throughout the class of birds) in those arrayed in 

 conspicuous tints the females are obscurely colored, in comparison 

 with the males. Yet to this rule there are exceptions, as notably 

 among the Jays, some of which do have "surprisingly gay and con- 

 spicuous colors," and among which both sexes are equally brilliant. 

 The shining black color of the Crows, the Raven, and some of the 

 Blackbirds are equally or (in the latter) almost equally shared by 

 both sexes, while the color is by no means well adapted to conceal- 

 ment. In many species the males, even when brightly colored, 

 share with the females the duties of incubation. This is the case 

 with the Rose-breasted Grosbeak, in which the male is most con- 

 spicuously colored, and who not only shares the labor of incubation, 

 but has the most injudicious habit of indulging in loud song while 

 sitting on the nest. In many of our ground-nesting Sparrows the 

 sexes, in respect to coloration, are wholly indistinguishable ; their 

 obscure colors, arranged generally in streaks and spots, are cer- 

 tainly in the highest degree protective; their nests, although not 

 domed, or even "covered," in the strict sense of the term, are gen- 

 erally most effectually concealed under tufts of herbage, and are 

 hence far better shielded from observation than the pensile, domed, 

 or bulky, covered nests that are regarded by our author as so highly 

 conducive to security through the concealment of the eggs and 

 young or the sitting female. 



Among the groups instanced by Mr. Wallace as building open 

 nests are " the extensive families of the Warblers (Si/tvi<i<f<r), 

 Thrushes (Turdidas), Flycatchers {Muadcapidce), and Shrikes (La- 

 nuxda )." While in a considerable proportion of the species of 

 these groups the males are " beautifully marked with gay and con- 



