THE YELLOW-POLL WOOD-WARBLER. 51 



birds, that seem, as it were, not to have been endowed with sufficient power 

 of flight to enable them to traverse a vast extent of country. Yet it proceeds 

 in summer as far as the 68th parallel, where it was found by Dr. Richard- 

 son in numbers and breeding. Although it comes into the United States 

 from the south at the early period mentioned, thousands follow in the wake 

 of the first that are seen in Louisiana, for, I met with great numbers during 

 the whole month of April, when on my way to the Texas, as well as after 

 my arrival in that country, where they threw themselves into all the bushes 

 along the sea-shore, apparently for the purpose of spending the night. At 

 this period they are quite silent, and many of them have not yet obtained the 

 reddish spots on the breast so conspicuous at a later season. 



Mr. Nuttall was the first naturalist who observed the very curious me- 

 thod in which it contrives to rid itself of the charge of rearing the young of 

 the Cowbird. "It is amusing," he' says, "to observe the sagacity of this 

 little bird in disposing of the eggs of the vagrant and parasitic Cow Troopial. 

 The egg deposited before the laying of the rightful tenant, too large for eject- 

 ment, is ingeniously incarcerated in the bottom of the nest, and a new lining 

 placed above it, so that it is never hatched to prove the dragon of the brood. 

 Two instances of this kind occurred to the observation of my friend Mr. 

 Charles Pickering; and last summer I obtained a nest with the adventi- 

 tious egg 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 shews 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 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 surpris- 

 ing ingenuity with which they often contrive to escape the burden of rearing 

 the offspring of the Cow Troopial, by burying the egg of the intruder. I 

 have known four instances in which single eggs have been thus buried by 

 the Yellowbird's building a second story to her nest, and enclosing the in- 

 truder 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 simi- 

 larly 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 Yellowbird raises only one brood 



