1889. | Faxon, Summer Birds of Berkshire County, Mass. 43 
burnian, Black-throated Blue, Black-and-yellow, Yellow-rumped, 
Tennessee, Mourning, and Canadian Warblers ; the White-throated 
Sparrow, Snowbird, Pine Finch, and Red Crossbill; the Olive- 
sided Flycatcher, and the Yellow-bellied Woodpecker. Under 
such conditions of compression there is naturally some inter- 
mingling of species representative of the two faune. Mr. 
Brewster* justly questions whether altitude be the sole factor 
regulating the distribution of birds on mountain slopes, and 
whether artificial causes, like the destruction of forests or the 
replacement of coniferous by deciduous trees, may not lead to a re- 
adjustment of faunal lines. This must be true especially in the 
case of a mountain of such moderate height as Graylock. | think 
that any one who has ascended this mountain by several routes 
will admit that the character of the surface and the vegetation 
have more to do with the distribution of the birds than temperature 
or other purely climatic conditions. If one should draw a line 
around the Saddle-Back range to indicate in a general way the 
limit of the Canadian faunal area, it would bear no closer relation 
to the altitudinal contour lines than do the isothermal lines across 
a continent to the parallels of latitude. Onthe North Adams side 
of the mountain the Canadian birds descend to a much lower 
level than they do in Williamstown. Not far from the North Adams 
Reservoir I found in some spruce and hemlock woods the Her- 
mit Thrush, Black-throated Blue, Black-and-yellow, and Canadian 
Warblers, and Snowbird, evidently on their breeding-ground, 
within about halfa mile of, and on the same level with the Yellow- 
breasted Chat, Towhee. and Brown Thrasher. The Wood 
Thrushes of the beech forest in the northern ravine of the Hopper 
compared with the Hermit Thrushes and other northern birds 
found at the same altitude on the opposite side of the ‘Mountain 
Pasture’ or height-of-land, afford another illustration of the influence 
of vegetation on the distribution of birds. When these mountains 
were in their primitive state and uniformly covered with forest, 
the correspondence between altitude and faunal regions was with- 
out doubt much closer than it is now. 
List oF BIRDS OBSERVED IN SOUTHERN BERKSHIRE (SHEFFIELD, 
AND VICINITY), JUNE 17-26, 1888. 
1. Actitis macularia. SPoTTED SANDPIPER.—A few seen on the Housa- 
tonic River. 
* Auk. I, p. 16. 
