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 yast extent of country. Yet it 
proceeds in summer as far as the 68th parallel, where it was found by Dr.. 
Richardson 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 
method 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 ejectment, 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 adventitious 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 or- 
phan 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 interest- 
ing 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- 
surprising ingenuity with which they often contrive to escape the burden of 
rearing the offspring of the Cow Troopial, by burying the egg of the intrud- 
er. 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 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, I hope, give to the world a drawing as well as a 
complete description of it. The Summer Yellowbird raises only one brood 
