Egberts and Bexner on the Ornithology of Minnesota. 11 



extreme difFei'ence of mean temperature at localities where this 

 species has been found breeding of from about twenty degrees 

 below to twenty degrees above freezing point. Can a similar in- 

 stance be named among any of our other birds 1 



Indeed, we might well question whether an organic type could 

 persist unchanged under a continuance of such diverse conditions, — 

 more diverse even as a single factor than those which serve to 

 produce races over greater geographical areas. It would certainly 

 seem that the period of incubation must vary under such diverse 

 conditions of environment, and why should not some physical result 

 (inappreciable in isolated cases) attend any constant variation in 

 time of the important period of embryonic development 1 



A CONTRIBUTION TO THE ORNITHOLOGY OF 

 MINNESOTA. 



BY THOMAS S. ROBERTS AND FRANKLIN BENNER. 



The material for the present paper is the result of a two weeks' 

 collecting trip in Grant and Traverse Counties, Minnesota, in the 

 early part of .lune, 1879. The principal point of observation was 

 at Herman, situated in the southwestern part of Grant Coimty, 

 and from it excursions were made to localities within fifteen or eigh- 

 teen miles. The notes of Traverse County were made on the way 

 to, and during a three days' stay at. Brown's Valley, situated some 

 forty miles west of Herman, between Big Stone Lake and Lake Tra- 

 verse, on the border of Dakota. These two localities, representing 

 as they do the prairie fauna of the State, possess very little timber, 

 and that only on the borders of some of the many lakes and pools 

 which abound in these counties. Herman, situated on the open 

 prairie, has no timber nearer than a mile and a half, where, around a 

 small lake, are a few large elm and oak ti'ees accompanied by the 

 usual underbrush of swamp-willows, alders, etc. Some fifteen miles 

 to the northeast are two lakes, the larger of which, called Elbow 

 Lake, is bordered by quite a large belt of timber, which proved to 

 be a very interesting field of observation. 



Brown's Valley, a trading-post, lies in a valley between the lakes 



