154 PACIFIC COAST AVIFAUNA No. 14 



uo definite dates of fall inig-ration though it proliably oi-cui's in August and 

 September. 



The nest lias been found in Fergus County, ^lay 29, 1901 (Silloway, 19():ia, 

 J). 66) ; also one on the Yellowstone, cited, above, for whieli the date is not given. 



299. Cinclus mexicanus unicolor IJonaparte 



DiPPEK 



A regular permanent resident, loeally common, in th(; western half of the 

 state. Breeds in the mountains of the Canadian and Upper Transition zones, 

 along clear mountain streams, on rocks or under bridges, preferably in the vicin 

 ity of waterfalls. Has been reported from all the mountain ranges, east to tlie 

 Helt Mountains (Williams, 1882a, p. 61), the Snowy Mountains (Silloway, 1903a, 

 p. 66), the Big: Horn Mountains (McChesney, 1879, p. 2385), and on Locate 

 Creek, Custer County (Cameron, 1908a, p. 51). The last is not in a trul.v moun- 

 tainous region, and it is the most eastern record in the state. The Dipper occurs 

 sometimes in the valleys and in the prairie region in wintei-. as at Le\visto^\-n 

 (Silloway, 1903a, p. 66). at Bozeman (Saunders, 1911a, p. 47). in the Bitterrool 

 Valley (Bailey, ]\IS). and at Race Track, Deer Lodge Valley, where I observed 

 one October 30, 1910, 



In the winter this species is not found in the same localities as in sunnner. 

 Streams occupied during the summer are liable to be frozen in \\ inter, the deep 

 pools where the birds obtain most of their food in the nesting season being too 

 still to remain open. In winter the Dipper prefers shallow rapids, rather than 

 waterfalls and jiools, the rapids keeping open throughout the (;old months. Th'- 

 movement from summer to winter haunts takes place in Octohej- and I\Iareh, and 

 constitutes the only migration undertaken by the species. 



Nesting begins in late Ma}', and lasts until xVugust, the birds probabl.v rais- 

 ing two broods. The earliest nest I know of was half-built on May 19, 1909. on 

 iJridger Creek, Gallatin County. This nest contained four eggs June 2. and 

 five June 5, when I collected it. I have also found a nest in process of construc- 

 tion in Gallatin County as late as June 21. and young leaving the nest were seen 

 •lul.v 20. At Trick Falls, Glacier National Park, birds were still feeding young 

 on Augu.st 4, 1914. 



300, Oreoscoptes montanus (J. K. Townsend) 



Sage Thrasher 

 A rare summer resident, found chiefly in the prairie region, but probably 

 originally found throughout the state in suitable localities. Records indicate 

 taat the species is rarer today than it was when the earlier ornithological work 

 was being done in the state, twenty years ago or more. There are but few records 

 from points other than in the prairie region, and only one west of the continen- 

 lal divide. Explicit records are as follows: Seen at rare intervals between the 

 Musselshell and Yellowstone (Allen, 1874, p. 49), Two on the Tongue River, 

 August. 1890 (Thorne. 1895. p. 218). Abundant on the Yellowstone ^Park 

 County, lietween Livingstone and Gardiner) in 1873 (Grinnell. 1876, p. 642). 



