\ 



154 PACIFIC COAST AVIFAUNA No. 14 



no definite dates of fall migration tlionyh it i)r'()t)at)ly occurs in August and 

 September. 



The nest has been found in Fergus County. :\Iay 29, 1901 (Silloway, liXK^a, 

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



299. Cinclus mexicanus unicolor l>onaparte 



Dipper 



A regular permanent resident, locally common, in the westei'U half of the 

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

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

 ity of watei-falls. Has been reported from all the mountain ranges, east to tlie 

 Belt ^fountains (Williams, 1882a, p. 61), the Snowy ^fountains (Silloway, 1903a, 

 p. 66), the Big Horn Mountains (^IcChesney, 1879, p. 2385), and on Locate 

 Creek, Custer County (Cameron, 1908a, p. 51). The last is not in a truly moini- 

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

 sometimes in the valleys and in the prairie region in winter, as at Lewistown 

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

 Valley (Bailey, MS), 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 summei-. 

 Streams occupied during the summer are liable to be frozen in w inter, the deej' 

 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 i)ools, the rapids keeping open throughout the cold months. Tiie 

 movement from sunnner to winter haunts takes place in Octobe)- and Mai-ch, and 

 constitutes the only migration undertaken by the species. 



Nesting begins in late ^la}^ and lasts until August, the birds probably rais- 

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

 liridger (,'reek, Gallatin County. This nest contained four eggs June 2, and 

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

 tion in Gallatin County as late as June 21, and young leaving the nest wer-e seen 

 July 20. At Trick Falls, Glacier National Park, birds were still feeding young 

 on August 4, 1914. 



300. Oreoscoptes montanus (d. K. Townsend) 



Sack Tjirasiikr 

 A rare sunnner resident, found chiefly in the priiirie ivgion. but [)robably 

 originally found throughout the state in suitable localities. Records indicate 

 tnat the species is rar-er today than it was when the earlier ornithological work 

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

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

 tal divide. p]xi)lieit 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, between Livingstone and Gardiner) in 1873 (Grinnell. 1S7(i, p. 642). 



