Tue ZooLocist—Aucust, 1876. 5017 
apparently firmer even than the twigs themselves. In separating a nest 
from the side of a chimney, I have known portions of the brick to which it 
was fastened to give way sooner than the cement with which it had been 
secured. When moistened, however, by long or heavy rains, the weight of 
their contents will sometimes cause them to part, and precipitate the whole 
to the bottom. The young birds cling’very tenaciously to the sides of the 
chimney, with their strong claws and muscular feet, and often save them- 
selves from falling in such accidents by this means, even at a very early 
age, and before they have attained their sight. As the nest, even when 
undisturbed, soon becomes too small for them, the* young leave it long 
before they are able to fly, and climb to the top of the chimney, where they 
are fed by their parents.” 
Birds are not given to adopt new fashions in building their nests 
hastily ; we believe that the ring dove has made its slovenly nest 
just in the same way time out of mind; while the longtailed tit 
has always been equally skilful and painstaking over the beautiful 
structure it devises for its numerous brood. Dr. Coues, however, 
is able to instance some cases where the nest-building instinct has 
been modified, and where birds have been induced, through certain 
reasons of advantage to themselves, to deviate from their usual 
plan. The cliff swallow (Tachycineta thalassina) has abandoned 
the cliffs in many places, and now prefers to attach its nest beneath 
the eaves of cottages. ‘The blue-headed Vireo (Vireo solitarius), 
a small flycatcher, according to Audubon, used to hang its nest 
between two twigs of a low bush, and construct it externally of 
gray lichens, internally chiefly of hair from the deer and racoon. 
In all nests of this species which have come under the notice of 
Dr. Coues the materials used have been almost exclusively— 
«Clusters of male flowers of Quercus palustris, which, having performed 
their allotted function, don their brownish hue at the very period when 
they can be utilized. Here is evidently a change within a moderately short 
period, rendered necessary by external causes. This necessity may have 
grown out of inability to procure the favourite materials, or a desire for self- 
preservation. In the case of the species under consideration, it cannot be 
denied that the utter inability, without unnecessary physical effort, to 
procure the hair of the afore-mentioned animals, particularly in sections 
where they have been compelled to retreat before the advance of man, may 
have been one of the causes which have induced the change. Iam satisfied, 
however, that it has not been the leading one, but that self-preservation has 
operated in this case for individual and family good. The adaptation of the 
