24 Allen on an Inadequate “ Theory of Birds' Nests.” 
the Canada Goose, that commonly nest on the ground, place their 
nests in bushes or trees in localities subject to sudden inundation. 
Many species, profiting by dearly bought experience, will abandon, 
in consequence of persistent persecution, long-occupied breeding- 
grounds for those more remote from danger. A remarkable in- 
stance of change in breeding habits from this cause is afforded by 
the Herring Gull, which, to escape its human foes, has been known 
to depart so widely from its usual habit of nesting on the open sea- 
shore as to place its nest in trees in more or less inland swamps. 
That birds have the power to grapple intelligently with unexpected 
emergencies has been repeatedly shown, a most striking instance be- 
ing afforded by the Baltimore Oriole, which has been observed to 
repair a half-demolished nest by weaving one end of a string into 
the weaker side and fastening the other end taut to a branch above. 
The fact that various species of Swallows, the Wren, Chimney Swift, 
and some other of our native birds which originally nested in de- 
serted Woodpeckers’ holes or hollow trees, abandon such nesting- 
sites for the better ones accidentally or intentionally provided by 
man, shows that they are by no means the slaves of “blind 
instinct,” but are able to take advantage of favoring circum- 
stances. 
The materials used by birds in forming their nests, it has been 
assumed, are those nearest at hand or most easy to obtain, or 
such as their peculiar habits chance to render them most famil- 
iar with, and that the mode of nidification depends upon their con- 
structive ability, — upon the “tools” with which nature has pro- 
vided them. This is undoubtedly to a great degree true, for it 
would be hard to conceive of the construction of an elaborate nest 
by any members of the Whippoorwill or Night-Hawk family, whose 
bills are excessively weak and small, and whose feet are unfitted for 
walking or perching, being barely able to support them on a flat 
surface. Hence we are not surprised that they place their eggs on 
the ground without the provision of a nest. Many other groups of 
birds are almost equally incapable of building nests. But among 
species equally furnished with the means for elaborate nest-making, 
there is the greatest diversity in the results of their architectural 
labors. Even when the materials employed by different species 
chance to be the same, the structures resulting from their use bear 
the impress of different architects. Nests of the same species also 
vary greatly at different localities in consequence of the materials 
