Altitudinal Range Shifts of Birds At the Southern Periphery of the Boreal Forest: 40 Years of Change In the Adirondack Mountains

Abstract

ABSTRACT.— Studies of geographic range shifts in response to climate warming that use data from Christmas Bird Counts or repeated state and provincial faunal atlases are better at detecting latitudinal shifts than altitudinal shifts because the coarse geographic scale of most citizen-science survey units masks the substantial elevational variation within their boundaries. To more directly measure altitudinal range shifts of forest-breeding bird species, we repeated an altitudinal transect survey conducted 40 years ago at Whiteface Mountain in the Adirondacks, New York, USA. We conducted roadside bird surveys at dawn and dusk at seven survey stations that ranged in altitude from 500 m to 1,425 m. We found considerable interspecific variation in the movement of altitudinal ranges, but document a preponderance of uphill shifts in both upper and lower boundaries of altitudinal breeding ranges. The shift of abundance-weighted mean altitudes for 42 species detected in both survey periods was +82.8 m. These shif...