Responses of Acadian Flycatchers (Empidonax virescens) to Hemlock Woolly Adelgid (Adelges tsucae) Infestation in Appalachian Riparian Forests

Invasive insects pose a significant threat to biodiversity, often affecting entire communities through the destruction of foundation species. Eastern Hemlock (Tsuga canadensis [L.] Carr.) forests, which are unique habitats in eastern North America, are threatened by an introduced insect, the Hemlock...

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Bibliographic Details
Published in:The Auk 2009-07, Vol.126 (3), p.543-553
Main Authors: Allen, Michael C, Sheehan, James, Master, Terry L, Mulvihill, Robert S
Format: Article
Language:English
Subjects:
Acadian Flycatcher
Adelges
Adelges tsugae
Agriculture
Animal nesting
Bird nesting
Birds
Defoliation
Eastern Hemlock
Empidonax virescens
Flycatchers
Forest habitats
Habitat preferences
Habitat selection
Hemlock Woolly Adelgid
Infestation
Insects
Invasive insects
Invasive species
Mortality
Nesting
Parks & recreation areas
Productivity
Riparian forests
Saplings
Studies
Survival
Tsuga canadensis
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Summary:Invasive insects pose a significant threat to biodiversity, often affecting entire communities through the destruction of foundation species. Eastern Hemlock (Tsuga canadensis [L.] Carr.) forests, which are unique habitats in eastern North America, are threatened by an introduced insect, the Hemlock Woolly Adelgid (Adelges tsugae Annand). Previous studies have found declines in the abundance of some forest bird species, including the Acadian Flycatcher (Empidonax virescens), with increasing infestation by Hemlock Woolly Adelgids. To identify potential mechanisms behind these declines, we studied abundance, breeding biology, and habitat selection of Acadian Flycatchers in 11 Eastern Hemlock-dominated riparian sites in Pennsylvania and New Jersey, representing a continuum of infestation levels, in 2001–2002 and 2006–2007. Eastern Hemlock supported 90% of all nests and was used more as a nesting substrate than expected at most sites. We found ∼70% fewer breeding pairs at heavily infested sites, though nest survival rates were not affected. The results suggest that Acadian Flycatcher populations in Eastern Hemlock forests may decrease with continued decline of Eastern Hemlocks. Populations in the Appalachian Highlands, where the species' association with Eastern Hemlock is most pronounced, may be at greatest risk.
ISSN:0004-8038
1938-4254
2732-4613
DOI:10.1525/auk.2009.08073