BIRDS OF BOULDER COUNTY, COLORADO 217 



Wilsonia pusilla pileolata, Pileolated Warbler (685a) 



Slimmer resident; common in the Mountain zone. Arrives on the plains 

 in migration, May 4-12 (3 records); leaves, September 15 — October 9 (4 records). 

 It has been noted at 9,000 to 10,000 feet at the end of May, and on the Plains as 

 early as August 27 in the fall. Gale took many sets of eggs between June 10 and 

 July 2, one at 11,000 feet. 



Setophaga ruticilla, Redstart (687) 



Migrant; apparently rare. The few records are for the Plains. Minot 

 observed it, May 31, 1880; Henderson, May 25, 1905; and the writer, August 24, 

 1909, and July 28, 1912. The last date was that of a female and indicates possible 

 breeding. Mr. Dean Babcock, of Estes Park, stated that he had seen the bird 

 there in migration (at about 9,000 feet). 



Family MOTACILLIDAE, The Wagtails 

 Anthus rubescens, Pipit (697) 



Summer resident; common above timberline. Arrives on the Plains in 

 migration, April 23-26 (2 records); leaves, September 22 (1 record). Noted 

 above timberline as late as September 15. Gale found nests above timberline 

 between June 29 and July 10; he also saw young birds near Gold Hill in August 

 and believed they nested in that vicinity (8,000 to 8,500 feet). 



Family CINCLIDAE, The Dippers 

 Cinclus mexicanus unicolor, Dipper (701) 



Permanent resident; in summer common along the streams of the Yellow 

 Pine and Mountain zones; in winter infrequent in the lower part of the Yellow 

 Pine and in the western part of the Plains. It has been noted a tittle above 

 timberline as late as September 4. Gale found eggs between April 28 and June 

 27. The writer saw young in the nest at 8,500 feet, July 28. 



Family MIMIDAE, The Thrashers, Mockingbirds, etc. 

 Oreoscoptes montanus, Sage Thrasher (702) 



Summer resident; rare along the base of the foothills; rather common in 

 fall migration on the Plains. Arrives, April 7 (1 record) ; leaves, September 

 24-25 (2 records). Though no nests have been taken in the county, the writer 

 observed them in July (9-21) in 1910, 1911 and 1912. In one case the birds 

 appeared to be in full song. The species has also been noted in the county by 

 Henderson, Dille and Young (Henderson). 



