Avian responses to forest disturbances in the Canadian Rockies

Disturbance regimes in the Canadian Rockies have changed substantially over the past century. Historically frequent, low intensity, patchy fires have been replaced by increasingly large, severe, and stand-replacing events, while the mountain pine beetle (MPB) outbreak has affected millions of hectares of forest since 1999. These shifts—driven by settler colonial fire suppression and anthropogenic climate change—have altered forest structure and composition, with uncertain consequences for wildlife. In particular, it remains unclear how bird communities—widely used indicators of ecosystem change— are responding to novel combinations of disturbance type, severity, extent, and recovery trajectories. My thesis investigates how birds respond to two broad-scale forest disturbances in the Canadian Rockies: high-severity wildfire and post-MPB outbreak management. Using data from autonomous recording units (ARUs), I analyzed avian species richness, community composition, and species-specific responses to disturbance types across different temporal and spatial scales. In Chapter 2, I assessed bird community responses to the 2017 Kenow Wildfire in Waterton Lakes National Park, using ARU data from 337 locations collected between 2018 and 2022. Elevation was the dominant predictor of avian community structure, but wildfire modified these patterns by amplifying species losses at mid-elevations, where bird communities may be more sensitive to disturbance. At lower elevations, fire effects were less pronounced—possibly due to generalist species or faster vegetation recovery—while high-elevation communities appeared relatively unaffected, potentially due to sparser pre-fire vegetation conditions. Species-level models showed varied responses, with mid-elevation old-growth forest specialists exhibiting the strongest declines. In Chapter 3, I examined bird communities across post-MPB-attacked forests in two regions that experienced temporally distinct outbreaks: a more recent outbreak in Jasper National Park (Jasper) and an earlier, historic outbreak in the Southern Rockies. Using ARU data collected in 2023 and 2024, I compared bird communities across three post-MPB-attack disturbance types: burned, harvested, and left-standing (n = 293). In Jasper, bird communities differed most clearly by disturbance type, whereas in the Southern Rockies, communities converged over time. Indicator species analysis revealed stronger and more distinct species associations in Jasper, while communities in the Southern Rockies showed possible legacy effects of wildfire. Together, these findings highlight how avian responses to disturbance are shaped by cumulative disturbance, elevation, and time, but also by the spatial configuration and scale of disturbance. Across both chapters, bird communities responded most strongly in landscapes where disturbance was spatially distinct, or applied in patchy mosaics. This research contributes to a growing body of work emphasizing the importance of heterogeneity and scale in shaping post-disturbance recovery, and supports forest management approaches that incorporate spatial and temporal variation to sustain biodiversity in dynamic mountain systems.

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