ROCK WREN. Salpinctes obsoletus obsoletus (Say)

Field characters.—Size nearly that of Junco; bill long and slender. Upper surface light grayish brown; under surface whitish, lightly flecked with dusky on breast; tail with a subterminal blackish bar and light tip. Body bobbed down and up at frequent intervals. Voice: Song a series of burred and clear notes of varying pitch, with occasional rests, chr, chr, chr, trr, ter, ter, eche, eche, chr, etc.; call note a clear tinkling trill.

Occurrence.—Common in summer at numerous points in the Yosemite section from near Merced Falls eastward across the Sierra Nevada to Williams Butte; ranges up to timber line; in winter disappears from the higher country, but remains all the year below level of heavy snow. Lives in rocky situations, either on broken outcrops or about masses of slide rock; also, in winter, on earth walls of gullies. Solitary.

The Rock Wren is one of a considerable group of birds and mammals whose local distribution is dependent upon the presence of a particular type of habitat. In the case of this bird the special requirement is met in bare, steep, or broken surfaces of rock or of hard-packed earth. The domes and rock slides of the high Sierras, the outcrops on the sides of the lower Merced Cañon, and the earth bluffs near Snelling afford suitable conditions for the species. In winter the mountains are deserted, the birds descending to lower levels or going south to the deserts; the numbers in the foothills, too, at this season become small.

The Rock Wren seems to be totally unaffected by conditions of temperature or humidity and is as much at home in the summer heat of the San Joaquin Valley as in the cool and rarified air of North Dome or Ragged Peak. The highest point at which it was seen was in Mono Pass, at about 10,500 feet altitude. Another high place of observation was near Vogelsang Lake, 10,350 feet. The species was observed in Yosemite Valley on August 31, 1917 (Mailliard, 1918, p. 19).

While in general features of structure and behavior a true wren, the Rock Wren presents some peculiarities which clearly adapt it to its particular kind of environment. In shape of body and head it is notably flattened, a feature which enables it to creep far into horizontal fissures and into crevices between boulders; the bill is very long and slender, enabling the bird to reach still farther, into remote niches, in its search for an insect or spider; the legs are short, but the sharp-clawed toes are very long, and have a wide span so that the bird can cling firmly to the vertical or even beetling rock wall; the coloration, in toto, is that of the average bare rock; when the bird is examined at close range the indistinct fine pattern of white and dusky dots and bars is seen to resemble, to a suggestive degree, the minute patterning of the rocks.

In size the Rock Wren is the largest of the wrens in the Yosemite avifauna, being more than half again the bulk of the next smaller, the Cañon Wren. From that species, which often occurs in the same territory as the Rock Wren, the latter may be known by its much paler coloration, lack of contrast in color of throat and rest of body, and by its longer, black-and-light-banded tail. The voices of the two are totally different.

In the lowland and foothill country, where birds in general are abundant, the Rock Wren might be easily overlooked through one's attention being absorbed by other species; but in the high mountains, especially on the granite domes and the heaps of slide rock where living things are much scarcer, this bird comes more readily to notice.

Like all wrens this bird is constantly on the move, turning to one side or the other at short intervals. It also bobs its body down and up spasmodically, in the manner of the Cañon Wren or of the American Dipper. When it is perched on a point of rock its repeated movements often carry it through a complete revolution in the course of a few seconds. During this turning and bobbing its short clear trills are uttered, and in spring its song is given.

The song is not set in character, being a series of syllables, repeated in irregular sequence, the successive series separated by short rests. One bird observed near Pleasant Valley sang 4 to 7 notes at a time, the intervals between being 5 or 6 seconds in duration. Chr, chr, chr, trr, ter, eche, eche, eche, were some of the 'words' in the song of this particular bird. The whole effort reminds one of the rambling song of the California Thrasher, but it is of much higher pitch.

No nest was found by us; but at Pleasant Valley on May 17, 1915, a pair of these wrens was seen carrying food beneath a large boulder near the Merced River. A bird observed in the same general locality on May 23 was similarly engaged, so the nesting season was probably at its height at this time. A family of young was seen abroad on a schist-like outcrop near Merced Falls on May 28, 1915.