142 PACIFIC COAST AVIFAUNA No. 14 



Found in the prairie region, mountain valleys and in the lower mountain can- 

 yons. 



Thi^ migrations take place in June and late August. Dates of spring arrival 

 are as follows: Gallatin t'ounty, June 18, 1909; C'hoteau, June 2'.i, 1912; Bitter- 

 root Valley, June S, 1911 (Hailey, MS). Fall departure: .Mill Creek, Deer 

 Lodge County, August 26, 1909; Gold Creek, Powell County, August 27, 1910; 

 Traill Creek, Park County, August 24, 1908. Five years at Bozeman average 

 September 16, with the latest September 29, 1912 (Oberholser, 1918, p. 222). 



Nesting takes place most commonly in July, though it is often begun soon 

 after the arrival of the species in June, and sometimes is delayed till August. 

 There are numerous records of the nesting, the earliest being June 24, 1900, at 

 Flathead Lake, the nest containing five eggs in which incubation had begi;n 

 ( Silloway, 1901a, p. 22), and the latest a set of eggs taken in the Rocky Moun- 

 tains along the forty-ninth parallel, August 19, 1874 (Coues, 1874b, p. 574). In 

 the average nest the eggs are laid during the first week in July, and the young 

 are on the wing early in August. Nesting appears to be somewhat (Earlier on 

 the west side of the divide than on the east side. 



268. Lanius borealis Vieillot 



Northern Shrike 



A winter visitor tliroughout the state, never very common, and irregular m 

 nunibers from year to year. Found chiefly in the Transition zone, but ma.v be 

 seen in open country in the Canadian in migrations. Reported by nearly all 

 observers who have done work in the winter months. 



This species arrives in October and leaves about the first of April. Outes 

 of arrival are: Custer County, October 16, 1906 (Cameron, 1908a, p. 49) ; Spiinu- 

 Hill, Gallatin County, October 6, 1908; Three Forks, October 17, 1909; Ana- 

 conda, October 23, 1910; Choteau, October 16, 1911; Kalispell. October 21. 1917 

 (Sloanaker, MS). Four years at Bozeman average October 27, with the earliest 

 arrival October 19, 1913 (Oberholser, 1918, p. 287). Dates of departure are: 

 Custer County, April 8, 1893, and March 26, 1904 (Cameron, 1908a, p. 49): 

 Lewistown, March 22, 1902 (Silloway, 1903a, p. 61) ; Bozeman, JIarch 31, 1909; 

 Bridger Creek, Gallatin County, March 19, 1911. Three years at Bozeman 

 average .March 30, latest April 3, 1912 (Oberholser, 1918, p. 287). 



269. Lanius ludovicianus excubitorides Sv.ainson 



White-rumped Shrike 



A common summer resident of eastern Montana, ranging westward to the 

 mountain valleys. Common in the eastern part of the state, becoming rarer 

 westward. The westernmost localities where it occurs are Gallatin County 

 (Richmond and Knowlton, 1894, p. 307), Teton and northern Lewis and Clark 

 counties (Saunders, 1914a, p. 140), Rocky Mountains, along northern border 

 (Coues, 1874b, p. 576), at Helena, and at Jlissoula. 



The migrations seem to be irregular. The species arrives on its breeding 

 grounds early in April, but migrant birds have been seen in the foothills of the 



