Modelling the Critical Habitat of the Bicknell’s Thrush in the Cape Breton Highlands

Abstract

Bicknell’s Thrush (Catharus bicknelli) is listed as a threatened species under SARA, and identification of critical habitat is a key priority in the species’ recovery. LiDAR data was used to create a habitat suitability model for the critical breeding habitat of the Bicknell’s Thrush (C. bicknelli) within Cape Breton Highlands National Park, where knowledge of the species distribution was limited to point-count survey records between 2002 and 2016, and songmeter records in 2017-18. The model identifies critical habitat as areas of dense, high elevation (>350 m) balsam fir dominated forest with a canopy height of ~four meters in height and stem density equal to or greater than 10,000 stems ha-1. Three habitat suitability models were created, identifying percent canopy closure between 2-3 m, 2-4 m, and 2-5 m in canopy height at elevations greater than or equal to 350 m. When compared to ground truthing data, photo classification, and forest composition data, it was found that while the model accurately identified balsam fir and spruce dominated forests and general trends in stem density (stems ha- 1), it did not accurately identify areas of good/excellent C. bicknelli habitat as determined through photo classification. Presence/absence data collected through songmeter recordings found no presence of C. bicknelli populations within the study area. However, presence of C. bicknelli populations was confirmed in more remote areas of Cape Breton Highlands National Park. While this model was not proven to be an effective method of identifying C. bicknelli critical habitat, it provides a starting point for future research. Further study is required in order to fine-tune the parameters of the model using LiDAR data spanning over the entirety of the Cape Breton Highlands. A model identifying critical habitat within the Cape Breton Highlands will be an important tool in prioritizing areas for monitoring and conservation of C. bicknelli breeding habitat and directing forestry practices in Cape Breton, as well as providing a framework for modelling habitat suitability for C. bicknelli in other areas of its range.