High Elevation Landbird Program 2002 Report

Whittam, Becky; Ball, Melanie

The High Elevation Landbird Program (HELP) was created by Bird Studies Canada (BSC) in 2002, to examine: 1) population trends of four migratory songbird species breeding at high elevations: Bicknell's Thrush (Catharus bicknelli), Fox Sparrow (Passerella iliaca), Swainson's Thrush (C. ustulatus) and Blackpoll Warbler (Dendroica striate); and 2) habitat preferences of the Bicknell's Thrush (a Species of Special Concern) in Atlantic Canada, especially on industrial forest land where the majority of the Atlantic population breeds. To collect information on population change, trained volunteers and BSC employees surveyed 22 pre-selected routes in Nova Scotia and 45 routes in New Brunswick once between the 4th and 28th of June using a standardized protocol. Each route was 1 km in length, with 5 stops each 250m apart. At each stop, surveyors listened silently for 5 minutes, then played a 30-second playback tape consisting of Bicknell's Thrush songs and calls, finishing with an additional 5 minutes of silent listening. Surveyors kept track of each individual bird heard or seen within the 10-minute survey period, as well as the direction and distance to each bird. BSC employees re-ran routes where Bicknell's Thrushes were not found during the first run to obtain a more precise indication of presence/absence of Bicknell's Thrush. In July and August, BSC employees measured habitat characteristics at all points where Bicknell's Thrush were detected, as well as at a random selection of points where Bicknell's Thrush were not detected (using only points from routes where no Bicknell's Thrush were detected on either of two runs). Swainson's Thrush was the most common target species found on survey routes with a frequency of detection of 91% in NB and 82% in NS, and a relative abundance of 11.2 birds per route in NB and 3.55 birds per route in NS. Bicknell's Thrushes were found on about 60% of routes in NS and NB, with a relative abundance of 2.2 birds per route in NB, and 1.09 birds per route in NS. Fox Sparrow and Blackpoll Warbler were found on roughly 50% of routes with relative abundances of about 1 bird per route for both NS and NB. Given the current number of routes (65), a preliminary power analysis revealed that it will take 30 years of annual surveys to detect a 3% decline in Bicknell's Thrush in New Brunswick and Nova Scotia. However, considering only surveys conducted in New Brunswick, it will take only 20 years of annual surveying to detect the same decline. The next step is to determine potential impacts of pre-commercial thinning on this species. Stem densities of spruce and fir at sites with Bicknell's Thrush are about 6000 stems/ha in NB and NS. Currently, thinning in NB is known to decrease balsam fir stem density to the range of that found at sites where Bicknell's Thrush are not present (2800 m2/ha), suggesting that thinning may impact this species' population. An indepth study of Bicknell's Thrush breeding biology on industrial forest land (planned for 2003) could better define the impact of thinning. Bicknell's Thrush was found at sites with higher density and basal area of balsam fir or spruce compared to sites without Bicknell's Thrush. In NB, Bicknell's Thrush was found at sites that were higher in elevation, had a greater proportion of mossy ground cover, and more dead trees than sites without Bicknell's Thrush. In NS, sites with Bicknell's Thrush had a significantly lower canopV height and lower density of deciduous trees, than sites without Bicknell's Thrush.