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Ecology and Demography of Bicknell's Thrush on East Mountain, East Haven, Vermont: Evaluating Potential Impacts of Wind Turbine Construction
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To establish baseline, preconstruction data for evaluation of the possible effects of wind turbine construction on montane forest bird populations on East Mountain in East Haven, Vermont, we conducted field studies in June and July of 2004. Focusing on Bicknell's Thrush (Catharus bicknelli), our primary research objectives were to: (1) estimate population size and density; (2) estimate demography and survivorship by sex and age class; (3) document reproductive success; and (4) spatially analyze adult thrush home range size, movement patterns and behavioral ecology. Our censusing and nest monitoring encompassed all avian species, while our mist-netting and banding targeted Bicknell's Thrush, Swainson's Thrush (Catharus ustulatus), Yellow-rumped Warbler (Dendroica coronata), and Blackpoll Warbler (Dendroica striata). Overall, we mist-netted and banded 198 individuals of the four target species, a capture rate of 8.9 new birds/100 net hours. We banded 10 male and 8 female Bicknell's Thrushes. We monitored 3 radio-tagged female Bicknell's Thrushes for the duration of the study period and calculated widely varying home ranges of 2.3 – 11.3 ha for each. Four of 7 radio-tagged females were depredated, probably by short-tailed weasels, within 1-5 days of release. We monitored a total of 12 active nests of 5 species; of 11 nests whose outcomes were known, 8 (73%) were successful. Our sample included 4 nests of 3 female Bicknell's Thrushes; 2 of these nests fledged young. We detected a total of 135 individuals of 16 avian species on two census dates, for a mean of 9.6 birds per point count. The suite of species was very similar to that found on other Vermont peaks, with the exception of 3 species typically restricted to lowland spruce-fir forests in the Northeast Kingdom: Black-backed Woodpecker (Piciodes arcticus), Gray Jay (Perisoreus canadensis), and Boreal Chickadee (Poecile hudsonica). We estimate that as many as 18-20 individual male Bicknell's Thrushes and 10-12 females may inhabit the full extent of suitable montane fir-spruce habitat on East Mountain. Our 2004 field work, while limited in scope and duration, provides a solid foundation for future research and monitoring.
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... Bicknell " s Thrush exhibits a skewed adult sex ratio across its breeding range, with males outnumbering females by a factor of approximately two (Rimmer et al. 2001a, Townsend et Table 9). The depredation of four radio-tagged females on East in 2004 (Rimmer and Faccio 2004) may have biased the 2005 and 4-year sex ratio. Regardless, the consistently male-biased adult sex ratio across the breeding range of Bicknell " s Thrush strongly suggests that females are experiencing disproportionate limitation at some point in the species " annual cycle. ...
It has been estimated that from 100 million to well over 1 billion birds are killed annually in the United States due to collisions with human-made structures, including vehicles, buildings and windows, powerlines, communication towers, and wind turbines. Although wind energy is generally considered environmentally friendly (because it generates electricity without emitting air pollutants or greenhouse gases), the potential for avian fatalities has delayed and even significantly contributed to blocking the development of some windplants in the U.S. Given the importance of developing a viable renewable source of energy, the objective of this paper is to put the issue of avian mortality associated with windpower into perspective with other sources of avian collision mortality across the U.S. The purpose of this paper is to provide a detailed summary of the mortality data collected at windplants and put avian collision mortality associated with windpower development into perspective with other significant sources of avian collision mortality across the United States. We provide a summary of data collected at many of the U.S. windplants and provide annual bird fatality estimates and projections for all wind turbines in the U.S. For comparison, we also review studies of avian collision mortality from other major human-made structures and report annual bird fatality estimates for these sources. Other sources also significantly contribute to overall avian mortality. For example, the National Audubon Society estimates avian mortality due to house cats at 100 million birds per year. Pesticide use, oil spills, disease, etc., are other significant sources of unintended avian mortality. Due to funding constraints, the scope of this paper is limited to examining only avian mortality resulting from collisions with human-made obstacles.
