Mountain Birdwatch Background

Bicknell's Thrush (Catharus bicknelli), recognized as a subspecies of the Gray-cheeked Thrush (C. minimus) since its discovery in 1881, was given full species status in 1995. Significant differences between the two taxa in morphology, vocalizations, genetics, and breeding and wintering distributions contributed to this designation. The new classification has led to the recognition of Bicknell's Thrush as one of the most at-risk passerine species in the eastern United States. Bicknell's Thrush is currently ranked by Partners in Flight as the top conservation priority among Neotropical migratory songbirds in the Northeast. The World Conservation Union considers the species vulnerable to extinction and has added it to the Red List of Threatened Species.

The breeding range of Bicknell's Thrush in the United States is limited to montane fir forests of New England and New York. In Canada it is found in highland spruce-fir forests in Quebec, Nova Scotia and New Brunswick. As a habitat specialist and the region's only endemic songbird, Bicknell's Thrush serves as a valuable indicator of montane forest health. Potential problems on the breeding grounds include atmospheric pollution (acid rain and mercury deposition), climate change, recreational development, communications tower construction, and wind power development. Since 1992, VINS has studied the distribution, ecology, and conservation status of Bicknell's Thrush in the northeastern United States. Similar efforts are underway in Canada.

Most of the wintering population of Bicknell's Thrush is found in wet, broadleaf forests of the Dominican Republic. These forests have been reduced to less than 8% of their historic extent in the last 30 years. VINS has conducted research and conservation in the Dominican Republic since 1994 to help address these problems.

Despite habitat loss on the wintering grounds and multiplying human impacts on the breeding grounds, few data are available to assess the conservation status of Bicknell's Thrush. Baseline and long-term data sets are needed to monitor population change across the species' breeding range. To fill the information gap, VINS enlists volunteers to survey montane forest sites in New York, Vermont, New Hampshire, and Maine. We coordinate our efforts with Bird Studies Canada's Atlantic Canada High-Elevation Landbird Program.

The Survey

Mountain Birdwatchers choose between two different survey protocols, depending on their bird identification skills. In Mountain Birdwatch Five Species, novice and intermediate birders concentrate on five focal species: Bicknell's Thrush (BITH), Swainson's Thrush (SWTH), Blackpoll Warbler (BLPW), White-throated Sparrow (WTSP), and Winter Wren (WIWR). This group contains both long-distance migrants (BITH, SWTH, BLPW) and short-distance migrants (WTSP, WIWR). It also includes species that only or primarily breed in montane forests (BITH, BLPW) and others found in mixed or conifer-dominated habitats at all elevations (SWTH, WTSP, WIWR). The songs and calls of these five species are learned through repeated study of the Mountain Birdwatch training tape. In Mountain Birdwatch FBMP, volunteers with advanced identification skills may choose to survey all species, in accordance with Forest Bird Monitoring Program protocols.

Surveys consist of 10-minute counts (formerly 5-minute counts) at each of five listening stations. Spaced at 250-m intervals, these stations form a 1-km route that passes through forests dominated by balsam fir (Abies balsamea), red spruce (Picea rubens), and heartleaf paper birch (Betula papyrifera var. cordifolia). A few routes pass through a transition zone and into upper-slope northern hardwoods. Mountain Birdwatchers use audioplaybacks (broadcasts of tape-recorded vocalizations) to improve the likelihood of encountering the elusive Bicknell's Thrush. This technique is employed only when the species escapes detection by point count or by chance. Mountain Birdwatchers double as "squirrelwatchers", keeping a tally of red squirrel observations along their routes. As the main nest predator in this habitat, red squirrels limit songbird reproduction every other year, when their numbers in high-elevation forests are elevated due to biennial booms in the cone crop.

Goals

Mountain Birdwatch Five Species and Mountain Birdwatch FBMP help advance three primary objectives.

1. To monitor populations of the montane forest birds of northern New England and New York.

2. To describe the influence of landscape and habitat features on avian distribution and abundance in montane forests.

3. To guide conservation efforts in high-elevation forests.
   

Although emphasis is placed on Bicknell's Thrush, records of all species are considered important and are examined carefully.

Five Species Survey Procedures

All Species (FBMP) Survey Procedures

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