Avian Response to Hemlock Woolly Adelgid in Southern New England

• Investigators: Rebecca Field, Glenn Motzkin, David Orwig, Morgan Tingley
• Contact: David Orwig
• Start date: 2000-06-01
• End date: 2001-08-31
• Location: Central Connecticut
• Latitude: +41.28 to +41.99
• Longitude: -72.73 to -72.25
• Elevation:
• Taxa: Adelges tsugae (hemlock wooly adelgid), Betula lenta (black birch), Catharus guttatus (hermit thrush), Dendroica fusca (blackburnian warbler), Dendroica virens (black-throated green warbler), Empidonax virescens (acadian flycatcher), Tsuga canadensis (eastern hemlock)
• Keywords: avian communities, bird surveys, black-throated green warbler, eastern hemlock, forest disturbance, hemlock woolly adelgid, point counts
• Release date: 2006
• EML version: knb-lter-hfr.85.2
• Revisions:
• Abstract:

  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. The study was conducted in a 4900 km2 study region extending from Long Island Sound northward to the southern border of Massachusetts and including the Connecticut River Valley in Connecticut, USA. Bird surveys were conducted at 40 points in 12 hemlock stands varying in HWA infestation and overstory mortality levels during the avian breeding seasons of 2000 and 2001. Ten-minute, 50-m radius point counts were used to survey all birds seen or heard at each point. Overstory and understory vegetation were sampled at each point. Indicator species analysis and non-metric multi-dimensional scaling were used to examine relationships between avian community composition and vegetation structure. 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.

• Methods:
• Use:

  This dataset is released to the public and may be freely downloaded. Please keep the designated Contact person informed of any plans to use the dataset. Consultation or collaboration with the original investigators is strongly encouraged. Publications and data products that make use of the dataset must include proper acknowledgement. For more information on LTER Network data access and use policies, please see: http://www.lternet.edu/data/netpolicy.html.

• Related datasets: HF021