Conservation of three forest landbird species at risk: Characterizing and modelling habitat at multiple scales to guide management planning

Abstract

To effectively conserve species at risk (SAR), it is important to understand their ecology at multiple scales, including stand-level habitat associations and landscape-level distribution. The Rusty Blackbird (Euphagus carolinus), Olive-Sided Flycatcher (Contopus cooperi), and Canada Warbler (Cardellina canadensis) are listed landbird species at risk (SAR) that breed in wet forest habitat in Canada’s Maritimes. To characterize their habitat for stand-scale conservation, I surveyed vegetation cover and structure at 99 known locations in the Southwest Nova Biosphere Reserve. Habitat at sites occupied by each SAR was significantly different from habitat at unoccupied sites. However, occupied habitat near recent forest harvesting (within 1 km) did not differ from that in unharvested areas, suggesting features can be retained in managed forest landscapes. I further categorized habitat using Nova Scotia’s Forest Ecosystem Classification (FEC) and found these SAR predominantly occupied the same wet-poor ecosites, potentially allowing for management of all three species as a suite. I also used FEC information to verify spatial data layers commonly used in forest management planning and found their accuracy ranged from poor to fair, depending on layer and buffer size considered.

To support regional-scale protected areas planning, I developed a species distribution model (SDM) for these species. I first evaluated 128 published SDM algorithms, finding that a majority did not accurately report model uncertainty, prediction metric, or both. To aid conservation practitioners in selecting and reporting on SDMs for conservation, I developed a guide based on data type, conservation objective, and experience. I then modeled the population density of the three SAR in four national parks in New Brunswick and Nova Scotia, using Poisson log-linear regression models with a branching hierarchy. When comparing predicted population sizes to regional population estimates, national parks supported habitat for only 3-4% of Canada Warblers and 1-2% of Olive-sided Flycatchers. Thus it is highly unlikely that existing national parks alone are able to maintain viable regional populations. To help prevent extirpation of these species, forestry prescriptions need to be adjusted to conserve habitat, and key locations for management should be identified at a regional scale.