Notice of Audubon's Birds of America. 135 



tions e%^ about two thirds buried, the upper edge only being 

 visible, so that, in many instances, it is probable that this species 

 escapes from the unpleasant position of becoming a nurse to the 

 sable orphan of the cowbird. She, however, acts faithfully the 

 part of a foster-parent when the egg is laid after her own.' 



" The following note from my friend Dr. T. M. Brewer, shows 

 that this little bird is capable of still greater exploits. 'There is 

 a very interesting item in the history of the yellow-poll warbler, 

 which has been noticed only within a few years, and which is 

 well deserving of attention, both for the reasoning power which 

 it exhibits, and for its uniqueness, for it is not known, I believe, 

 to be practiced by any other bird. I allude to the surprising in- 

 genuity with which they often contrive to escape the burthen of 

 rearing the offspring of the cow troopial, by burying the egg of 

 the intruder. I have known of four instances in which single 

 eggs have been buried by the yellowbird. and building a second 

 story to her nest and enclosing the intruder between them. In 

 one instance, three of the Sylvia's own eggs were thus covered 

 along with that of the cow blackbird ; and in another, after a 

 blackbird's egg had been thus concealed, a second was laid, 

 which was similarly treated, thus giving rise to a three storied 

 nest. This last you have in your possession, and will, 1 hope, 

 give to the world a drawing, as well as a complete description of 



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IT ' Tt* •??• W TV "TP Tt" 



" The fabric alluded to above may be thus described. A nest 

 of the usual form had been first constructed, of which the exter- 

 nal diameter was three inches. It is composed of cotton rudely 

 interwoven with flaxen fibres of plants, and lined with cotton of 

 a reddish color, with some hairs round the inner edges. The egg 

 of the cowbird having been deposited in this nest, another of a 

 larger size, three inches and three quarters in external diameter, 

 has been built upon it, being formed of the same materials, but 

 with less of the flaxen fibres. The egg is thus surmounted by a 

 layer three quarters of an inch thick, and was discovered by 

 opening the lower nest from beneath. It is agglutinated to the 

 lining of the nest, having been addled and probably burst. In 

 this second nest a cowbird had deposited an egg, which was, in 

 like manner, covered over by a third nest, composed of the same 

 materials, and of nearly the same size as the second." 



