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.

本研究探讨了长期受铁杉球蚜（Adelges tsugae Annand; HWA）侵染导致的东部铁杉（Tsuga canadensis (L.) Carr.）衰退与消亡对鸟类群落组成的影响。上层林冠铁杉死亡率与鸟类群落组成高度相关。东菲比霸鹟（Contopus virens）、褐头牛鹂（Molothrus ater）、簇山雀（Baeolophus bicolor）、白胸䴓（Sitta carolinensis）、红眼莺雀（Vireo olivaceus）、罩林莺（Wilsonia citrina）以及多种啄木鸟类的种群丰度，在铁杉死亡率超过60%的样点中达到最高。黑喉绿林莺（Dendroica virens）、阿卡迪亚霸鹟（Empidonax virescens）、黑胸林莺（Dendroica fusca）与隐夜鸫（Catharus guttatus）则与受铁杉球蚜侵害极少或未受侵害的完整铁杉林强相关。东部铁杉具备独特的结构特征，可为美国东北部的众多鸟类提供重要栖息生境。因此，铁杉球蚜引发的铁杉消亡对鸟类群落产生了深远影响。在新英格兰南部地区，黑喉绿林莺、黑胸林莺与阿卡迪亚霸鹟与铁杉林关联极强，是对铁杉消亡尤为敏感的物种。而罩林莺作为一种受区域关注的物种，实际上可能会从高铁杉死亡率伴生的密集幼苗层中获益。