December 3 or 5, noon – 2:00pm, via Zoom
Nicole Mooradian
Dr. Andrew Laughlin
McCullough Fellowship: Department of Environmental Science
The eastern hemlock (Tsuga canadensis) is a foundation tree species that provides important habitat and foraging opportunities for many organisms. Since the introduction of the hemlock woolly adelgid (HWA) (Adelges tsugae) in the 1950s, hemlocks have been under threat across their range, showing accelerated declines in the Southern Appalachians, where effects of the adelgid may be amplified by a recent lack of harsh winters. Studies from northeastern North America have shown that hemlock-associated
avian species have declined in areas of high hemlock mortality. This study investigated how avian communities in the Southern Appalachians have been affected by the loss of this important tree in a region that is ecologically distinct from those of previous studies.
Avian point count surveys were conducted in the Great Smoky Mountains National park to describe current avian abundance and diversity as compared with historic surveys. Vegetation surveys assessed the current size and health of hemlocks at each site to
develop an index of hemlock decline since before HWA reached the Southern Appalachians. Results show that sites with high hemlock mortality are significantly less similar in bird species composition between current and historical surveys than sites of low hemlock mortality, indicating that species composition has shifted more in areas with greater hemlock decline. Data suggest that, in response to hemlock decline, generalist and disturbance-adapted birds such as the Brown Creeper, Certhia americana, have increased in abundance, while hemlock-associated species, such as the Acadian Flycatcher (Empidonax virescens) have decreased. While there is no evidence for the strong obligate relationships observed in the northeast, findings suggest that hemlocks in the Southern Appalachians are an important tree for several avian species and further decline of hemlocks could continue to alter the composition of bird communities in this region.