1921 



BIRDS OF MONTANA 



151 



Spring migration takes place in late ]\Iay. About .May 25 in Custer and 

 Dawson counties (Cameron, 1908a, p. 51). Specimens from Miles City are dated 

 :\ray 25 and 28, 1902 (Hedges, coll. Univ. Montana). There are no dates on 

 record later than July, and, therefore, nothing to indicate when the fall migra- 

 tion takes place. 



Nesting begins in June. A nest containing three eggs and a cowbird's was 

 found in Custer County, on the Yellowstone River, June 11, 1894 (Cameron, 

 1908a, p. 51). A nest with four eggs was found between Forts Union and Ben- 

 ton, June 19, 1860 (Cooper, 1869b, p. 295). 



294. Wilsonia pusilla pusilla (Wilson) 



Wilson Warbler 

 A migrant in the eastern part of the state, probably mainly, if not entirely, 

 in the prairie region. One male taken at Fort Keogh, ^lay 19. 1889 (Thorne, 

 1895, p. 218). A breeding bird taken at Upi)er Two :\Iedicine Lake. Teton 

 County, August 5, 1914, is an intergrade between this form and pileolata. 





\ 



Fig. 32. Nest axd eggs of Pileolated Wakblei:. 

 Pipestone Basin, Jefferson County; June 16, 

 1910. Nest beneath the roots of a wh.low. 



295. Wilsonia pusilla pileolata (Pallas) 



Pileolated Warbler 



A connnon summer resident of the mountains in the western half of Mio 



