86 BULLETIN 203, UNITED STATES NATIONAL MUSEUM 



may at certain times and places be as multitudinous in the liigli 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 Corapositae 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 planta- 

 tions — 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 Rio 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. 



"Tennessee warblers pluck the tiny, white protein corpuscles from 

 the brown, velvety bases of the long petioles of the great-leafed 

 Cecropia trees, taking advantage of these dainty and apparently 

 nutritious tid-bits when the usual Azteca ants fail to colonize the 

 hollow stems; for only on trees free of ants does this ant-food 

 accumulate in abundance. 



"Wliile the Tennessee warbler departs during February from some 

 districts where it is common in midwinter, it remains until April 

 in regions where the dry season is not severe. After the middle of 

 April it is only rarely seen in Central America; and there appears 

 to be no record of its occurrence in May." 



DISTRIBUTION 



Range. — Canada to northern South America. 



Breeding range. — The Tennessee warbler breeds north to south- 

 western Yukon (Burwash Landing and the Dezadiash River) ; 

 southern Mackenzie (Mackenzie River below Fort Wrigley, lower 



