BIRDS OF BOULDER COUNTY, COLORADO 213 



Hirundo erythrogastra, Barn Swallow (613) 



Summer resident; common on the Plains and less so in the Yellow Pine 

 and Mountain zones. Abundant in the fall migration on the Plains. Arrives, 

 April 21-27 (3 records); leaves, September 15-29 (4 records). Gale found eggs 

 from June 15 to 28, and also noted a second laying on August 3 at an elevation of 

 about 8,000 feet. 



Iridoprocne bicolor, Tree Swallow (614) 



Summer resident; infrequent in the Mountain zone. Possibly occurs on the 

 Plains in migration, though all records for the region are from the mountains 

 (9,000 feet, Tolland; 9,000-10,000 feet near Ward; 9,000 feet, Long's Peak Inn). 

 Gale observed nest-building on May 31 and found eggs from June 12 to 17; the 

 nest sites were abandoned woodpecker holes. The writer noted it on May 29 at 

 Tolland. 



Tachycineta thalassina lepida, Northern Violet-green Swallow (615) 



Summer resident; common from the edge of the Plains at Boulder to the 

 middle of the Mountain zone. Arrives, May 4-13 (4 records); leaves, August 13 

 — September 9 (3 records). Gale found eggs at about 9,500 feet (Beaver Park), 

 July 10-20. 



Riparia riparia, Bank Swallow (616) 



Summer resident; common locally on the Plains. Arrives, April 24 (1 record, 

 Gale). The writer observed a colony nest-building on May 19, 1912, and incu- 

 bating June 12, 1910. Birds were still at their nesting-sites, July 27 and August 

 13 (the latest date seen). 



Stelgidopteryx serripennis, Rough- winged Swallow (617) 



Summer resident ; infrequent on the Plains. Probably occurring also in the 

 Yellow Pine, as a pair was observed at Estes Park (7,500 feet) by Widmann in 

 June, 1910. Arrives, May 8-12 (2 records); latest fall date August 14. The 

 writer observed them entering small caves in a sandstone cliff and also preparing 

 a hole in a river bank, but has no dates for eggs. 



Family BOMBYCILLIDAE, The Waxwings 



Bombycilla garrula, Bohemian Waxwing (618) 



Winter resident; rather erratic in its movements though common at times 

 in the Yellow Pine and Mountain zones. First fall dates are November 6 and 

 December 6; leaves, March 13 — April 8 (6 records). Henderson noted a flock 

 of 150 on February 13, 1905. It has frequently been observed feeding on the 

 berries of the juniper and kinnikinnick. 



