"Similar to _D. c. caerulescens_, but adult male darker above, especially the pileum, which is not lighter blue than the back, the latter usually more or less spotted or clouded with black, sometimes chiefly black, the pileum sometimes streaked with black; adult female darker and duller olive above and less yellowish beneath, with the olive of flanks darker and more strongly contrasted with the pale olive-yellowish of abdomen." In discussing its distribution, he was unable to define its breeding range with any degree of accuracy; and adds in a footnote: "On the whole, the form is not a very satisfactory one, one of the two characters on which it was based (smaller size) failing altogether (_D. c. cairnsi_ averaging slightly larger, in fact, than _D. c. caerulescens_), and the other only partially so, since many specimens of _D. c. cairnsi_ have little if any black on the back, while many of _D. c. caerulescens_ have quite as much as the average amount shown in _D. c. cairnsi_." The 1931 A. O. U. Check-List gives the breeding range of _cairnsi_ as from Maryland to Georgia, but no definite line can be drawn; birds from southern Pennsylvania and Maryland, and perhaps the Virginias, are variably intermediate in their characters, and specimens can be found that are referable to either one or the other form. Before this race had been separated from the northern form, Cairns (1896) wrote of its haunts: High up on the heavily timbered mountain ranges of western North Carolina is the summer home of the Black-throated Blue Warbler. Here in precipitous ravines, amid tangled vines and moss-covered logs, where the sun's rays never penetrate the rank vegetation and the air is always cool, dwells the happy little creature, filling the woods from dawn to twilight with its song. * * * These birds are a local race; breeding from one generation to another. They arrive from the south nearly ten days earlier than those that pass through the valleys on their northward migration. It is common to observe migrants through the valleys while breeders on the higher mountains are already nest-building and rearing their young. This statement agrees with Professor Cooke's (1904) later data, and with his statement: "The species is one of the few that appear in the mountains earlier than on the plains, and the case seems to sustain the theory that the individuals of a species that breed farthest south are the first to migrate in the spring." _Nesting._--Cairns (1896) writes on this subject: