PACIFIC NIGHTHAWK. Chordeiles virginianus hesperis Grinnell

Field characters.—Body size that of robin, but with much longer and more slender wings; these when closed reach to end of tail or beyond. Similar to poor-will in many respects. Chin and narrow band across middle of longer wing feathers, white; rest of plumage barred or spotted with brown, gray, black, and white, in mixed pattern, giving a neutral effect. Flight erratic, with many quick turnings. Voice: A one- or two-syllabled note, zee-nt, or pee'-ark.

Occurrence.—Summer visitant in small numbers to higher open country (Canadian and Hudsonian zones on west slope, and Transition east of Sierran crest). Observed in 1915 at Merced Lake August 25; Vogelsang Lake August 30; Tuolumne Meadows July 5, 7, and 27; and at Williams Butte September 15; Paoha Island, Mono Lake, July 3, 1916; and on ridge 3 miles east of Coulterville, August 9 and 11, 1920. Reported in Yosemite Valley June 28 and 29 and August 24, 1920. Active chiefly in evening and morning; forages high in the air. Spends most of daytime resting lengthwise on large horizontal limbs of trees.

The Pacific Nighthawk is a summer visitant to the higher parts of the Yosemite region. It begins its forays for insects at sundown or soon after and continues its activity well into or through the hours of complete darkness. In July, when the young probably have hatched out, the adult birds forage in the daytime as well. For instance 2 or more were seen abroad foraging over Tuolumne Meadows about 9:30 on the morning of July 27, 1915.

The nighthawk is provided with a wide gaping mouth which enables it to capture flying insects with facility; the long and narrow wings and tail enable the bird to fly rapidly and to turn quickly when in pursuit of moths, flying ants, or other insects which frequent the upper air.

From time to time a Pacific Nighthawk while flying at a considerable height will suddenly drop into an abruptly downward swing with wings held above the back in V-shape. As the bird checks its flight and darts upward, a rushing noise is heard, resembling the syllable 'whoof.' Whether or not this is produced by the wings we do not know.

At Williams Butte on September 15, 1915, 5 nighthawks were seen in flight high overheard about 4:15 P.M.; these were probably in migration, as none was seen after that date in places where they were observed earlier in the season.

Six or more of these birds, actively engaged in foraging, were noted near the crest of the ridge 3 miles east of Coulterville on August 9 and 11, 1920. None was seen in this locality, which is at the lower margin of the Transition Zone, in June of 1915, so those seen later in the season were probably 'vagrants.'

In Yosemite Valley a pair of these birds flew low over the river on the stormy evenings of June 28 and 29, 1920; and during a heavy storm on August 24, 1920, a lone bird coursed for two hours up and down over the Merced River (C. W. Michael, MS).