BIRD STUDY 29 
They are able to defend themselves. Birds that make their 
nests in cavities, like Woodpeckers, Kingfishers, Bluebirds and 
some Swallows, show little difference in color between the 
sexes, and in several of these cases the females are highly 
colored. 
While there are many exceptions, birds are generally col- 
ored like their surroundings. The whole Vireo family, for ex- 
ample, is olive green or greenish gray, and these birds are 
scarcely noticed as they flit through the trees and gather food 
from the leaves. The large Warbler family migrates north- 
ward in blossom time, when the splashes of yellow and white 
in their bluish gray plumage seem simply to add so many 
more blossoms as they flit through the trees. When they re- 
turn in the autumn the blossoms have disappeared and their 
bright spots have been greatly obscured. 
Prairie Chickens and Grouse can scarcely be seen in up- 
land grass or stubble field. The Ruffed Grouse, both by col- 
oration and rigid attitude, looks like the stump beside which 
he stands. Woodcocks and Quail are the color of the dry 
leaves in which they hide. All Snipes are the color of dried 
grass beside which or in which they run. The American Bit- 
tern can with difficulty be distinguished from the cat-tail be- 
side which he stands; and the Great Blue Heron is almost 
indistinguishable when viewed against the rushes. 
The study of coloration in birds’ eggs is very interesting 
and very perplexing. In the wild there would seem to be a re- 
lation between the color of a bird’s egg and the color of the 
bird that lays it. Among barnyard Chickens it is not so. All 
hens lay white eggs whether they themselves are white, buff, 
dappled gray or black. And yet, as we know, some hen’s eggs 
are whiter than others. 
But a Crow lays just such an egg as you would expect a 
Crow to lay—a smoky, darkly blotched egg. The Cowbird has 
an egg of similar character. All Blackbirds’ eggs have a dusky 
ground color and are variously spotted and splashed with 
black. The Orioles, which are are brighter colored Starlings, have 
lighter colored» eggs, which are not so heavily spotted and 
