Avian Response to Hemlock Woolly Adelgid in Southern New England 2000-2001

This study examines changes in avian community composition associated with the decline and loss of eastern hemlock (Tsuga canadensis (L.) Carr.) resulting from chronic hemlock woolly adelgid (Adelges tsugae Annand; HWA) infestations. Overstory hemlock mortality was highly correlated with avian community composition. Abundance of eastern wood-pewee (Contopus virens), brown-headed cowbird (Molothrus ater), tufted titmouse (Baeolophus bicolor), white-breasted nuthatch (Sitta carolinensis), red-eyed vireo (Vireo olivaceus),hooded warbler (Wilsonia citrina), and several woodpecker species was highest at points with greater than 60% mortality. Black-throated green warbler (Dendroica virens), Acadian flycatcher (Empidonax virescens), blackburnian warbler (Dendroica fusca), and hermit thrush (Catharus guttatus) were strongly associated with intact hemlock stands that exhibit little or no mortality from HWA. Eastern hemlock has unique structural characteristics that provide important habitat for numerous bird species in the northeastern U.S. As a result, removal of hemlock by HWA has profound effects on avian communities. Black-throated green warbler, blackburnian warbler, and Acadian flycatcher are very strongly associated with hemlock forests in southern New England and appear to be the species that are particularly sensitive to hemlock removal. The hooded warbler, a species whose status is of regional concern, may actually benefit from the development of a dense seedling layer associated with high hemlock mortality.