TREE SWALLOW. Iridoprocne bicolor (Vieillot)

Field characters.—Body size about that of Linnet or Junco; tail nearly square-ended. Upper surface of body black with a steely blue iridescence; whole under surface white; no white on rump. Voice: Faint single notes, seet, sometimes given several together to form a weak twitter.

Occurrence.—Sparse summer visitant. Recorded only in vicinity of Snelling and Lagrange, and, east of the mountains at Mono Lake Post Office. Usually near standing water. In pairs or loose companies.

The Tree Swallow resembles the Violet-green Swallow in general plan of coloration and in habits, but it does not range so high altitudinally as does the latter species, nor was it anywhere so abundant. We found the Tree Swallow in May and June along the lower reaches of the Merced and Tuolumne rivers west of the foothills, and in the neighborhood of Mono Lake, beyond the Sierras.

The Tree Swallow is, perhaps, more prone to perch than other swallows. A pair will be seen a good deal of the time sunning themselves on twigs of the dead tree in which their nesting site has been chosen. The nest is hidden as a rule within an old woodpecker hole in some tree standing at the edge of quiet water.