SAGE THRASHER 427 



certain Pacific-side species have extended in the opposite direction." 

 Its habits are probably similar to those of the northern race. 

 The measurements of 17 eggs average 27.1 by 19.6 millimeters; the 



eggs showing the four extremes measure 30.2 by 20.0, 25.2 by 20,2, and 



24.9 by 18.7 millimeters. 



OREOSCOPTES MONTANUS (Townsend) 



SAGE THRASHER 



PlATES 87-90 



HABITS 



The above scientific name and the old common name, mountain 

 mockingbird, are both misnomers, as this is not a mountain bird and is 

 not a mocker. But sage thrasher is a most appropriate name, for it 

 designates the bird's habitat and its relationship to the true thrashers. 

 It is the characteristic bird of the vast sagebrush plains, and its dis- 

 tribution is limited almost entirely to the semi arid regions where 

 immense areas are clothed with practically nothing but a waving 

 sea of pale, gray-green sage {Artemisia tridentata) . Only the great 

 sagehen, now rapidly disappearing, seems to show such partiality for 

 the sagebrush plains. Though confined mainly to the valleys and 

 mesas, this thrasher extends its range in many places up intp the foot- 

 hills, where the sage gives way to other bushes, junipers and mahogany 

 woods, up to 4,000 feet or even 6,000 feet at some places; this is as 

 near as it comes to being a mountain bird. 



The 1931 Check-list gives its range as north to southern British 

 Columbia and central Montana. It has evidently extended its range 

 more or less irregularly during the past ten years. We did not record 

 it in southern Saskatchewan in either 1905 ,or 1906, but Laurence B. 

 Potter, of Eastend, of the same general region in which we worked, has 

 sent me several notes on its occurrence there from 1933 to 1939. He 

 says : "Sage thrashers made their first known appearance in this south- 

 ern part of Saskatchewan during the long period of drought, lately 

 ended, and the first specimen was secured in 1933. Rather unexpect- 

 edly, it has continued to migrate north since the wet seasons have set 

 in. The sage thrasher is generally associated with the hot, arid plains, 

 and it seemed strange to find it singing lustily on a cold, wet morning, 

 as on May 8, 1938." He wrote to me on September 23, 1934, that his 

 friend Charles F. Holmes took a breeding male in 1933 and the next 

 year shot a breeding female and found a nest with eggs. On June 

 12, 1934, Fred Bard found a nest with a set of five eggs and took both 

 birds ; later on he found two m.ore nesting pairs. The thrashers came 

 there quite early in May in 1938 and 1939. Whether this is to be a 

 permanent extension of the breeding range remains to be seen. 



Courtship. — ^The first mention of the courtship activities of the sage 



