BIRDS OF BOULDER COUNTY, COLORADO 221 



July 4, 191 2) ; in winter common in the lower part of the Yellow Pine and along the 

 edge of the Plains. Gale found eggs between May 19 and June 29, mostly at 8,500 

 to 9,500 feet. The nests were placed under ledges or in mine shafts. 



Hylocichla fuscescens salicicola, Willow Thrush (756a) 



The only record for the county is that of a nest taken by Gale, June 13, 1884, 

 near Gold Hill; later in his notes, however, he describes the same nest as being 

 that of a Wood Thrush. Widmann saw several of this species near Long's Peak 

 Inn, 9,000 feet (only a short distance north of the county line), in July, 1910, and 

 Dean Babcock informed the writer that they were frequently seen there in the 

 summer of 191 2. It has probably been overlooked in the county, though it does 

 not appear to be common in Colorado. 



Hylocichla ustulata swainsoni, Olive-backed Thrush (7580) 



Summer resident ; common along the creeks in the upper part of the Yellow 

 Pine and the lower part of the Mountain zone. Arrives on the Plains, April 16 — 

 May 12 (5 records). Recorded in the fall, September 13 and October 19 (Gale). 

 The same observer found eight nests between June 23 and July 18. In the vicinity 

 of Estes Park, Widmann observed them along the streams from 6,000 to 9,000 

 feet. 



Hylocichla guttata guttata, Alaska Hermit Thrush (759) 



Sprague took a specimen (the first for the state) on October 6, 1895, at Mag- 

 nolia. As the species appears to be a regular migrant in the eastern part of the 

 state (Sclater), it is not unlikely that, since Sprague's observation, it has been 

 overlooked in the county. 



Hylocichla guttata auduboni, Audubon's Hermit Thrush (759a) 



Summer resident ; common in the Mountain zone and infrequent in the upper 

 part of the Yellow Pine. Arrives on the plains and in the mountains, May 13-30 

 (4 records); leaves the plains, October 21-22 (2 records). Gale found many sets 

 of eggs between June 10 and July 12 at 8,500 to 10,000 feet. The writer has seen 

 it from near timberline down to about 8,000 feet in the first week of July. It holds 

 first place among the birds of the county as a songster. 



Planesticus migratorius propinquus, Western Robin (761a) 



Permanent resident; abundant in summer in the Plains and Yellow Pine 

 zones and common in the Mountain zone, occurring up to timberline; in winter 

 infrequent in the Yellow Pine and along the edge of the Plains. The full tide of 

 spring migration occurs about the last of March at which time birds may be found 

 at 9,000 feet. The fall migrants leave in the latter half of October. Gale found 

 eggs between May 7 and July 17 from the Plains to near timberline. Many birds 

 show a considerable amount of white at the corners of the tail and probably not 

 all are typical of the western subspecies. 



