"I think 'coffee warbler' would be a name far more appropriate than Tennessee warbler for this plainly attired little bird; it was merely a matter of chance that Alexander Wilson happened to discover the species in Tennessee rather than at some other point on its long route from Canada to Central America; but the warblers themselves manifest a distinct partiality to the coffee plantations. The open groves formed by the shade trees, whose crowns rarely touch each other, yet are never far apart, seem to afford just the degree of woodland density that they prefer. It matters not whether these trees are Grevilleas from Australia with finely divided foliage, or Ingas with large, coarse, compound leaves, or remnants of the original forest--a mixture of many kinds of trees with many types of foliage: from Guatemala to Costa Rica the Tennessee warblers swarm in the coffee plantations during the months of the northern winter and are often the most numerous birds of any species among the shade trees. Possibly they may at certain times and places be as multitudinous in the high forest as in the plantations. Although I have never found them so, the negative evidence must not be allowed to weigh too heavily, for such small, inconspicuous birds, devoid of bold recognition marks, are not easy to recognize among the tops of trees over a hundred feet high. "Tennessee warblers are fond of flowers, especially the clustered heads of small florets of the Compositae and Mimosaceae, and of the introduced Grevillea that sometimes shades the coffee plantations. They probe the crowded flower clusters, perhaps seeking small insects lurking there rather than nectar. The white, clustered stamens of the Inga--the most generally used shade tree of the coffee plantations--are especially attractive to them. Local movements within their winter range appear to be controlled by the seasonal abundance of flowers. So, in the valley of the Río Buena Vista in southern Costa Rica, at an altitude of about 3,000 feet, I found Tennessee warblers very abundant during December and January. Here they flocked not only in the forest and among the shade trees of the little coffee groves, but also in great numbers through the second-growth thickets that filled so much of the valley, where at this season there was a profusion of bushy composites with yellow or white flower-heads, and of acacia-like shrubs (_Calliandra portoricensis_) with long, clustered, white stamens. But during February, the third dry month, the thickets became parched and flowered far more sparingly. Now the Tennessee warblers rapidly declined in numbers, and before the end of the month disappeared from the valley. During the following year, which in its early quarter was far wetter, a number remained through March, and a few well into April.