Allen on an Inadequate “Theory of Birds Nests.” 31 
chief enemy of these birds is man, by whom they are robbed of 
their eggs in a most brutal and wholesale way. The species that 
breed in deep crevices in the rocks almost wholly escape the rapacity 
of their human foes, the eggs being almost invariably, it is said, 
placed beyond reach, while those (some of the Guillemots) that de- 
posit their eggs on the surface are robbed almost to extermination. 
The dull, thoroughly protective colors of the Burrowing Owls, of 
which there are several species, render them often difficult objects 
to discover even when wholly exposed, yet they nidificate in de- 
serted marmot holes, and there find security against the attacks of 
predatory skunks and foxes, to which they would be exposed if nest- 
ing on the ground, — usually the only other alternative in the 
localities they inhabit. In fact, instances might be multiplied in 
which the breeding of birds in holes in trees, or in the earth, or in 
otherwise concealed nests, might be explained more rationally than 
by the theory of concealment of a brightly colored female parent, — 
the basis of Mr. Wallace’s ingenious “Theory of Birds’ Nests,” — 
namely, security from enemies through other means than simply 
concealment. 
Mr. Wallace, in commenting on “ What the Facts Teach us” in 
relation to this theory, argues that the differences in color between 
the sexes in birds that build an open nest may have been brought 
about by the bright-colored females being weeded out or eliminated 
in consequence of being more exposed to the attacks of enemies, 
since any modification of color which rendered them more conspic- 
uous would lead to their destruction and that of their offspring, 
while the attainment of inconspicuous tints would tend to their 
preservation. Hence this theory is intimately connected with, or 
in part based upon, Mr. Darwin’s theory of “ sexual selection,” 
which Mr. Wallace at this time accepted, but which he has recently 
had the better judgment to discard as an inadequate explanation of 
sexual differences in color among animals. 
The most surprising thing about Mr. Wallace’s “ Theory of Birds’ 
Nests ” * is its inadequacy, and its irrelevancy to the facts it was 
proposed to explain, and in this respect it is scarcely excelled by any 
of the crude inventions into which the more ardent supporters of the 
* I wish to here state explicitly that I refer in these remarks wholly to Mr. 
Wallace's “Theory of Birds’ Nests,”, and not to his most admirable essay on 
“The Philosophy of Birds’ Nests,” which is replete with sound sense, and to 
nearly every syllable of which I most heartily subscribe. 
