170 



PACIFIC COAST AVIFAUNA 



grass (■(luntry of this region lies in the Upper Hoiioran. It is eoiiiinon in this 

 zone in migrations, liowever. 



Tlie migrations take place in ]\[areh, and in October or November. The 

 average date of arrival at Terry is March 25, the earliest, March 20, 1903 ; the 

 average at Columbia Falls is March 23, with the earliest, March 9, 1895 (Cooke. 

 1907, p. 205). Other dates are: Spring Hill, Gallatin County, March 19, 1909, 

 Creniian Gnlch, Silver Bow County, March 10, 1910; Helena, March 12, 1911, 

 Lubec, March 28, 1912; Poison, March 10, 1913; Bitterroot Valley, March 4, 

 1910, March 14, 1911, March 11, 1912, and February 26, 1913 (Bailey, MS). 

 Fall migration dates are: Columbia Falls, November 6, 1896 (Cooke, 1907, p. 

 205) ; Cinnabar Basin, Park County, October 25, 1908; Pipestone Creek, Jeffer- 

 son County, October 7, 1909. Fall dates for this species are rare, for the bird 

 seems to become inconspicuous for some reason after early August. My I'ecords, 



Fig. 35. Male Mountain Br.UKnmi) 

 AT NEST. Pipestone Creek, Jsr- 

 FERSON County; June 20, 1910. 



kept ilaily for five years, show that the Mountain Bluebird was seen veiy seldom 

 in September and October. 



Nesting begins normally, early in ilay. I found a pair starting to Iniild a 

 nest in a cabin in Sunday Gulch, Silver Bow County, April 5, 1910, but the nest 

 was not completed, and in that year the spring was exceptionally early. At 

 ('hoteau birds were building nests on May 10, 1912, and the first egg was laid 

 May 14. I have seen birds feeding young in Bozeman by May 29, 1911, and the 

 first young are usually on the wing by June 15. Second l)rood nests begin the 

 latter part of June. I have seen birds of one pair nest building June 21, 1910, 

 when another pair were still feeding young of the first brood in the nest near-by. 

 r have seen young just out of the nest late in Jul.v. bat I believe the nesting is 

 eiitirel.v over by earl,y Augu.st, as tlie birds flock in the mountains about that 

 time. They may often be found at high elevations, in the stunted timber of the 

 iliidsonian zone, with the first cold snap in the first week of August. 



