Mesohabitat Use of Threatened Hemlock Forests by Breeding Birds of the Delaware River Basin in Northeastern United States
Ross RM, Redell LA, Bennett RM, Young JA. 2004. Mesohabitat Use of Threatened Hemlock Forests by Breeding Birds of the Delaware River Basin in Northeastern United States. Natural Areas Journal. 24(2004):307-315
Eighty fixed-point radius plots were established in which territories of breeding birds were estimated on four forest-terrain types in Delaware Water Gap NRA. Four insectivorous species showed high affinity for hemlock forest type and exhibited significantlly greater numbers of territories in hemlock than hardwood sites. These species are at risk from continued hemlock decline in the Delaware River Valley. Avian biodiversity may be at risk in eastern parks and forests due to continued expansion of the hemlock woolly adelgid (Adelges tsugae), an exotic homopteran insect native to East Asia. To assess avian biodiversity, mesohabitat relations, and the risk of species loss with declining hemlock (Tsuga canadensis) forests in Appalachian park lands, 80 randomly distributed fixed-radius plots were established in which territories of breeding birds were estimated on four forest-terrain types (hemlock and hardwood benches and ravines) in the Delaware Water Gap National Recreation Area, a National Park Service unit on the Delaware River in both Pennsylvania and New Jersey, USA. Both species richness and number of territories were higher in hardwood than hemlock forest types and in bench than ravine terrain types. Four insectivorous species, Acadian flycatcher (Empidonax virescens), blue-headed vireo (Vireo solitarius), black-throated green warbler (Dendroica virens), and Blackburnian warbler (Dendroica fusca), showed high affinity for hemlock forest type and exhibited significantly greater numbers of territories in hemlock than hardwood sites. These species are hemlock-associated species at risk from continued hemlock decline in the Delaware River valley and similar forests of the mid-Atlantic east slope. Two of these species, the blue-headed vireo and Blackburnian warbler, appeared to specialize on ravine mesohabitats of hemlock stands, the vireo a low-to-mid canopy species, the warbler a mid-to-upper canopy forager. Unchecked expansion of the exotic adelgid and subsequent hemlock decline could negatively impact 3600 pairs from the park and several million pairs from northeastern USA hemlock forests due to elimination of preferred habitat.
- Type
- Journal Article
- Authors
- Ross, Robert; Redell, Lori; Bennett, Randy; Young, John
- Units
- DEWA
- Keywords
- acadian flycatcher (Empidonax virescens), avian biodiversity, Birds, blackburnian warbler (Dendroica fusca), black-throated green warbler (Dendroica virens), blue-headed vireo (Vireo solitarius), Breeding Birds, Forest Management, hemlock forests, Hemlock Woolly Adelgid
- Subjects
- Ecological Framework: Biological Integrity | Focal Species or Communities | Forest/Woodland Communities , Ecological Framework: Biological Integrity | Focal Species or Communities | Birds