1921 BIRDS OF MONTANA 63 



vvlun'e extensive ornithological wm-k has heen done exc'('i)t Flathead l/ike. It is 

 evidently much eominouer on the prairies ol' the i-astern half ot the state tliau in 

 the mountain valleys of the western halt'. It nests in the I'pper Sonoran and 

 Transition zones, never in the mountains, hut only in the valle.\'s of Iowcm- foot- 

 hills. It breeds most commonly in eottonwood troves along streams, hut also in 

 evergreens growing along the foothills. 



Dates of nesting: The earliest date for eggs iu the state is ;\hiy 7, in Custer 

 County (Cameron, 1913, p. 17l)). Silloway records a set of three with ir.euha- 

 tion advanced on ^lay !), 190:5 (l!)(i:ia. pp. 29-80). Cameron gives .June '21 as 

 tlie latest date he has seen eggs, and I'oues (1874b, pp. 625-626) records eggs at 

 the forks of the Milk River, July 16, 1874. According to my experience the 

 majority of birds do not nest until after the middle of May, and nests uuiy be 

 found most commonly in June. The young are out of the nest and able to fl.v 

 at any time from the first of July to the last of August. 



Migration dates: Gallatin Valley. April 17, 1909. Silver liow.Api'i! 8, 

 1910 (Saunders, 1914a. p. 25). Cameron records a large flight of about 2000 

 birds iu Custer County, iu April, 1890 (1907, p. 263). Fall dates s^eni very 

 irregular. Cameron states that the birds leave soon after the young are able to 

 fly. The only fall dates which 1 have are Sun River, September 27, 1912 

 (1914a, p. 132), and P.ridger Mountains, November IS, 1908. 



115. Archibuteo lagopus sancti-johannis (Gmelin) 



R(U'<i]i-LEG(!ED Hawk 



A winter visitor in the mountain valleys and on the ju'airies. Comniou 

 locally, and ai^parently distribute(l through most of the state, liut not i-eported 

 from the Bitterroot Valley nor from Fergus County. I have found it abundant 

 in winter in the Gallatin Valley (1911a, p. 36), rare in Teton County (1914a, 

 p. 132), and have not observed it in southwestei-n Montana. In Custer and Daw 

 son counties it is reported common, but becoming rare (Cameron. 1907, pp. 

 2()3-264). It is also reported from Fort Custer in February, 1878 (AleChesney, 

 1879, p. 2391), and from the vicinity of Billings in winter (Thomas, ]MSi. 



There are a number of sununer records of this species, and it possibl.v bi'ecds. 

 or formerly did so. Cameron records a nest found in the badlands in .May, of 

 which the identification is doubtful. Common in sununer at Flathead Lake 

 (Silloway, 1901a, p. 46) ; abundant at Gardiner at the end of August (Griunell, 

 1876, p. 649). 



^ligration: In the Gallatin Valley this specii's first aii|H'ared October 9, 

 19(18, and was last seen April 17, 190!). 



116. Archibuteo ferrugineus (Lichtenstein) 



FebRUGI.NUIS K(U'GU-LEr, 



An .-iliundant summer resident of the prairies in the eastern |iart of the 

 state. Less common in valleys of the mountains, and rather rare west of the 

 continental divide. Nearly all observers record it in the eastern regions. It is 

 rep(u-ted to winter in the eastern i)art of the state, in Custer and Dawson coun- 



