This is a species which, in its external appearance, is so closely allied to the Wood Pewee, and the Small Green Crested Flycatcher, that the most careful inspection is necessary to establish the real differences existing between these three species. Its notes, however, are perfectly different, as are, in some measure, its habits, as well as the districts in which it resides.

The notes of Traill’s Flycatcher consist of the sounds wheet, wheet, which it articulates clearly while on wing. It resides in the skirts of the woods along the prairie lands of the Arkansas river. When leaving the top branches of a low tree, this bird takes long flights, skimming in zigzag lines, passing close over the tops of the tall grasses, snapping at and seizing different species of winged insects, and returning to the same tree to alight. Its notes, I observed, were uttered when on the point of leaving the branch. The pair chased the insects as if acting in concert, and doubtless had a nest in the immediate neighbourhood, although I was unable to discover it. It being in the month of April, I suspected the female had not begun to lay. Five of the eggs in the ovary were about the size of green peas. I could not perceive any difference in the colouring of the plumage between the sexes, and I have represented the male in that inclined and rather crouching attitude which I observed the bird always to assume when alighted.

I have named this species after my learned friend Dr. THOMAS STEWART TRAILL Of Edinburgh, in evidence of the gratitude which I cherish towards that gentleman for all his kind attentions to me.

Many specimens of this Flycatcher were procured by Mr. TOWNSEND about the Columbia river, several of which are still in my possession, after giving one to the Prince Of MUSIGNANO, who had not seen one before, and another to the Earl of DERBY.