144 PACIFIC COAST AVIFAUNA No, 14 



ward with t:icainsoni. ReL'orded as follows: Foi't Keogh, breeds, young taken 

 July 24 (Tliorne, 1895, p. 218) ; Custer and Dawson counties, common migrant, 

 noted May 16, 1899 (Cameron, 19()8a, p. 49) ; Miles City, six skins dated from 

 .May 11 to June 8, 1902 (Hedges, coll. Univ. Montana). The last mentioned spe- 

 eimeus have recently been compared by Dr. Bishop and myself with birds in the 

 former's collection. They are typical of the eastern race. 



27.5. Vireosylva gilva swainsoni (Baird) 



Western W.vkbling Vireo 



A couimon summer resident throughout the western part of the state, inter- 

 grading eastward, in the prairie region, with gilva. Breeds in cottonwood groves 

 of the prairie region and mountain valleys, and in aspen groves of the moun- 

 tains, in the Transition and Canadian zones. Occurring up to 70(10 feet in the 

 southern part of the state, and to 651)0 in the northern, Rci,)orted by all ob- 

 servers, and one of the commonest summer liirds in the mountains, whei'c it is 

 particularly characteristic of the aspen groves. 



The migrations take place in May and August, the species arriving about the 

 middle of May at low elevations, but in the mountains often no+ until June. At 

 I'olumbia Falls, three years give May 16 for the average and May 14, 1895, the 

 earliest (Cooke, 1909b, p. 80). Other dates are Bozeman, June 1, 1909; German 

 Gulch, Silver Bow County, May 28, 1910; Bozeman, May 28. 1911: Bitterroot 

 \'alley. May 6. 1911 (Bailey, MS). Fall dates are: Bozeman. August 10, 1908, 

 and August 16, 1909; Gold Creek, Powell County. August 27, 1910; Belton. Aug- 

 ust 27, 1915 (DuBois, MS). 



Nesting takes place in June and Jul.v. The earliest nest on record is one 

 at Flathead Lake containing three fresh eggs June 15. 1900, Another at this 

 same localit.y contained three young June 23, 1900 (Silloway, 1901a, p, 19), 

 The latest nest I have record of is one on Little Pipestone Creek, Jefferson Coun- 

 ty, whicii contained four eggs July 13, 1910, 



274. Lanivireo solitarius cassini (Xantus) 



Casstn Vireo 

 A summer resident in the northwestern part of the state, west of the con- 

 tinental divide, occurring rarely in migration east of the divide in the moun 

 tains. Breeds chiefly in the Transition, in Douglas fir and tamarack forests. 

 Records: First reported from the state from Columbia Falls (Cooke, 1909b, p. 

 168), where the average arrival is April 28, the earliest April 26, 1895, and a 

 date of fall migration, September 12, 1895. Breeds at Flathead Lake eommonl.y 

 (Saunders, 1915b, p. 111). A nest at Yellow Bay, Flathead Lake, found partly 

 built June 22, 1916. The .young flew July 25 (Sloanaker, MS). Taken at 6000 

 ieet near Corvallis, September 10, 1909, by Vernon Bailey (Bailey. .MS). Sev- 

 eral seen on Willow Creek, Powell County, September 12 and 13, 1910 (Saun- 

 ders, 1912a, p. 30). One seen on the West Fork of the Sun River, east of the 

 continental divide. September 3, 1912 (Saunders. 1914a. p. 141^. 



