Roberts and Benner on the Ornithology of Minnesota. 11 
extreme difference 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 'I 
» 
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 June, 1879. The principal point of observation was 
at Herman, situated in the southwestern part of Grant County, 
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 trees 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 
