YELLOW-POLL WARBLER. 455 



attention, both for the reasoning powers which it exhibits, and for its 

 uniqueness, for it is not known, I believe, to be practised by any other 

 bird. I allude to the surprising ingenuity with which they often con- 

 trive to escape the burden of rearing the offspring of the Cow Troopial, 

 hy burying the egg of the intruder. I have known four instances in 

 which single eggs have been thus buried by the Yellow-bird's build- 

 ing 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 Black-bird, and in another, after a Black-bird'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, I hope, give to the world a drawing as well 

 as a complete description of it. The Summer Yellow-bird raises only one 

 brood in the season in Massachusetts. The eggs, four or five in num- 

 ber, measure 5i eighths in length, by a trifle more than half an inch 

 in breadth ; they are of a light, dull, bluish- white, thickly sprinkled with 

 dots and small markings of various sizes of dull reddish-brown, accu- 

 mulated towards the great end." 



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

 usual form had been constructed, of which the external diameter was 

 three inches. It is composed of cotton rudely interwoven with flaxen 

 fibres of plants, and lined with cotton of a reddish colour, with some 

 hairs round the inner edges. The egg of the Cowbird having been de- 

 posited 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 disco- 

 vered 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 also 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. 



All our little birds known by the name of Warblers, and referred 

 by authors to the genera Sylmcola, Trichas, and Vermivora, present the 

 same structure in their digestive and respiratory organs. Their oeso- 

 phagus is rather narrow, without dilatation ; the proventriculus bul- 

 biform, with numerous oblong glandules ; the stomach rather small, ob- 

 lique, elliptical or i-outidish, with the lateral muscles distinct, but of 



