ROUGH-WINGED SWALLOW. Stelgidopteryx serripennis (Audubon)

Field characters.—Body size about that of Linnet or Junco; tail almost square-ended. Whole upper surface dull brown; throat and chest grayish brown; belly and feathers below base of tail white. No brilliant or iridescent markings whatsoever. Voice: Three or four weak notes, zeetle-tzeet, repeated at irregular intervals.

Occurrence.—Sparse summer visitant in foothills west of Sierra Nevada. Observed by us only at following points: 2 miles southwest of Lagrange, on Blacks Creek west of Coulterville, and near Bower Cave. Recorded once in Yosemite Valley, May 22, 1903 (Widmann, 1904, p. 70), when two were seen over Sentinel Meadow in company with Violet-green Swallows. Frequents vicinity of gulches having steep earth banks. In pairs or small companies.

The Rough-winged Swallow is the most local in its manner of occurrence of the several species of swallows found in the Yosemite section. Previous to 1919 it escaped our attention entirely, and subsequently was found at only three places in the western foothills, as noted above. The species differs from all of our other swallows as regards nesting site. It chooses a steep earth bank and there digs a horizontal tunnel in which to place its nest. There its spotless, white eggs and later the young are entirely hidden from view.

At Blacks Creek, one mile west of Coulterville, eight Rough-winged Swallows were seen on the morning of May 10, 1919. There were suitable nesting sites close by but the birds seemed not as yet to have settled down for the rearing of broods. They were flying about, sometimes coming to rest on dead weed tips or bare branches of trees; at times they alighted directly on the dry sandy earth of a cow trail.

From time to time the males were seen in pursuit of the females and, while so engaged, to make rather striking use of their seemingly plain garb. They would spread the long white feathers (under tail coverts) at the lower base of the tail until these curled up along either side of the otherwise brownish tail. The effect produced was of white outer tail feathers, such as those of the junco or the pipit. Males can by means of this trick be distinguished from the females at a distance of fully 50 yards. An examination of specimens in hand reveals the fact that the under tail coverts of the males are broader and longer than those of the females.

A nest of this swallow was found by Mr. Donald D. McLean on Jordan Creek near Bower Cave on June 20, 1920. It consisted of a mass of dry grass placed in an excavation in an earth bank and contained three eggs.