Habitat occupancy by Spruce Grouse (Canachites canadensis) in the south of its range in Quebec, Canada

Studying habitat occupancy at the margins of the distributions of species can be helpful in clarifying the requirements of species and planning management measures. Spruce Grouse (Canachites canadensis (Linnaeus, 1758)), a bird species associated with northern short-needle coniferous forests in North America, has its southeastern range limit where coniferous forests are mixed with temperate deciduous forests and agricultural lands. Some isolated populations are found in these habitats. Using a single-season occupancy modelling approach, we investigated habitat use by Spruce Grouse, accounting for imperfect detection, in the lowlands of the St. Lawrence River in southern Quebec, Canada. We conducted call-response surveys of Spruce Grouse over three years at 279 sites (59 sites in 2007, 100 sites in 2008, and 120 sites in 2009). At the site level, the probability of occupancy was 21% (95% confidence interval (CI) = 10.7%–37.9%) and probability of detection was 54% (95% CI = 34.7%–73.0%). Based on the covariates in the models, occurrence increased with higher cover of coniferous trees and low deciduous shrubs, and decreased with higher cover of deciduous trees. Finally, detection probability was highest at the beginning of the survey (50% in late April) and was influenced by year.