The Museum. 
* 
Vol. I. PHILADELPHIA, MAY, 1885. No. 1. 
For The Museum. 
RARE AND CURIOUS BIRDS’ NESTS. 
BY PROF. THOMAS G. GENTRY. 
From time immemorial, it has been the current popular belief that birds of the 
same species never varied their style of architecture, but constructed the same form of 
nest, and out of the same materials, as their remotest progenitors did, instinct being the 
principle by which they were guided. This opinion, though long since exploded by 
science, is still, I am sorry to say, entertained by those who should know better. An 
examination of nests from different and widely separated localities affords evidence 
sufficient to convince the most skeptical of persons of its erroneousness. The most 
marked differences will be noticeable in the composing materials, as these will be found 
to vary with the environment, and in a wider degree in the nests of some, than in those 
of otherj species. Even the configuration, which is less prone to change, is often influ¬ 
enced by the circumstances of position and latitude. 
Among the thrushes, the robin is the most addicted to variation, and this is not 
wholly confined to the constituents of his usually mud-plastered domicile, but is fre¬ 
quently to be observed in the arrangement thereof, and in the contour and position as 
well. In Southern New Jersey, where low marshy woods abound on the outskirts of 
towns and villages, robins build nests which contrast most markedly with what we are 
accustomed to see in more northern localities. The great masses of a grayish-green 
fibrous lichen, which hang from tree and shrub in those sylvan marshes, are freely utilized 
by them, and its very nature to mat, when pressed together, precludes the necessity 
of using mud. 
In the summer of 1877 m y attention was directed to a nest of this species which 
was built upon a railroad embankment. The ground had an inclination of forty-five 
degrees. To one not conversant with the facts, such a position for a structure of the 
kind these birds are known to make, would appear impossible. Difficult as the task 
must seem to be, when viewed from a human standpoint of judging of the builders’ 
capabilities, it was nevertheless accomplished, and in this wise: A semi-circular wall of 
mud, some three inches in height, was, after much labor, erected, and within the cavity 
thus formed was placed a coarse, substantial and bulky fabric. 
