408 Wetmore, Birds of Lake Burford, N. Mex. [July 



almost passing within reach, so that I heard the soft click of their bills 

 as they seized their prey. On calmer days they circled high in the air 

 or at intervals returned to sweep down over the sage. Occasionally in 

 early morning I saw them resting in little flocks in the sun in the tops 

 of still leafless cottonwoods. By June 2 the flocks of these swallows had 

 retired to the hills where they were found about the limbs of dead yellow 

 Pines inspecting woodpecker holes with much chattering and flying about. 

 The birds then often hovered in the air with rapidly moving bills, the 

 males seeming to endeavor to seize the females by the feet, or the feathers 

 of the abdomen, while others circled about calling excitedly. Cold storms 

 during the first week of June frequently brought them back in flocks to 

 feed over the flats but when the sun came out again they disappeared once 

 more in the hills. After June 7, though fairly common in the gulches 

 above, comparatively few came down along the shore of the lake. 



S3. Stelgidopteryx serripennis (Audubon). Rough-winged Swal- 

 low. — Single individuals were observed on May 24 and 25, and a pair 

 was found in an arroyo near the cabin on June 8. 



84. Vireosylva gilva swainsoni (Band). Western Warbling 

 Vireo. — These Vireos were found in the thickets lining the gulches and 

 among groves of aspens. They were not observed until June 2 but prob- 

 ably arrived two days or more earlier, as I found one pair on that date 

 with a nest partly constructed in a chokecherry tree (Padus melanocarpa) . 



85. Lanivireo solitarius plumbeus (Coues). Plumbeous Vireo. — 

 The Plumbeous Vireo was common among the Yellow Pines in the hills 

 above the lake on May 26, and was noted on all of my subsequent work in 

 areas suited to it. On May 26, males were in full song, and one was ob- 

 served carrying a bit of nesting material about with it and singing at the 

 same time. The birds were found entirely in the Yellow Pines and often 

 ranged in the tops of the tallest of these. They continued in full song 

 until the middle of June and then became more silent. Some of the call 

 notes given by this bird reminded me of the chattering calls of Lanivireo 

 flavifrons while many notes introduced into the song were similar to some 

 of the phrasing used by the White-eyed Vireo. 



S6. Vermivora virginiae (Baird). Virginia's Warbler. — This war- 

 bler was common among the thickets of small oaks in the gulches and on 

 the higher slopes around the lake, but was so secretive that it was difficult 

 to observe. The males often sang from the tops of tall yellow pines, where 

 they chose a hidden perch and remained motionless. When disturbed 

 by some one moving about below they flew off for some distance, some- 

 times remaining in the pines and continuing to sing, or again pitching 

 down into the undergrowth where they were hidden from sight. The 

 song varied somewhat but usually could be identified without particular 

 trouble. An incubating female was shot on June 16. The callnote of 

 this species is a sharp emphatic chip, but though the birds scolded at me 

 frequently it was seldom that they came out in sight to do so. 



