Effect of boreal forest disturbance due to logging at different spatial scales on migratory songbirds

Abstract

Boreal birds have experienced population declines that may be related to alteration of the forest at a range of scales. Understanding how resource extraction may affect the distribution and abundance of species is critical to address conservation policy in the boreal forest region. This study aims to understand how habitat alteration by logging influences the abundance and habitat choices of a migratory songbird, the Canada Warbler (CAWA; Cardellina canadensis) in its Canadian breeding range and more specifically within the northwestern region of Ontario, where there is little information about this species at risk. I assess whether there exists a different response in the abundance of upland migratory songbirds to logging disturbance at different scales. Also, I assessed the “habitat compensation hypothesis,” which states that some species can substitute their primary habitat for other alternative and less preferred habitats on the landscape. I conduct a meta-analysis of 21 studies to identify the effects of habitat alteration on a relative abundance index (RAI) of 21 upland songbird species, comparing logged to unlogged sites along the southern border of Canadian boreal forest. Using generalized linear mixed models (GLMM), I model the RAI incorporating two scales (local- and landscape-scale effects), time since logging, and forest type. Several species, including CAWA, are reported in decline in Canada. They occasionally have a higher mean RAI comparing logged areas at landscape scale than comparing at the finer local scale, suggesting that they occupy lower quality habitats in disturbed areas. The results are consistent with other findings: birds associated with old-growth forests are most sensitive to logging, as well as birds that nest on trees and those more associated with a coniferous forest. I then assess how time since logging affects CAWA occurrence and distribution in Northwestern Ontario. I use Maxent software to develop a predictive highresolution (30 m) field-validated species distribution model (SDM). [...]