Thesis Defence: Owl habitat suitability in burned forests

Steffani Singh, supervised by Dr. Karen E. Hodges, will defend their thesis titled “Owl habitat suitability in burned forests” in partial fulfillment of the requirements for the degree of Master of Science in Biology.

An abstract for Steffani Singh’s thesis is included below.

Defences are open to all members of the campus community as well as the general public. Registration is not required for in-person defences.

Abstract

Human-driven climate change has increased the frequency and severity of wildfires globally. Owls are vulnerable to habitat changes caused by fire and post-fire management like salvage logging. As fires reshape landscapes, understanding how heterogeneity and management in burned forests contribute to long-term owl persistence is crucial. I evaluated four key aspects of owl habitat use in burned forests: (1) owl presence in burned forests of different ages and severity classes compared to unburned forests, (2) owl presence in recent, severely burned patches, (3) owl habitat selection of specific vegetative features within burned forests, and (4) the influence of post-fire salvage logging on owl occupancy. In 2023–2024, I conducted passive acoustic surveys for owls in burned (≤20 years post-fire) and unburned forests in British Columbia. I characterized forest habitat through vegetation surveys and GIS data, and modelled the presence of owl species against forest characteristics. I detected eight owl species in burned and unburned forests, of which six were modelled. Owls demonstrated species-specific habitat use in burned forests. Four owl species used burned and unburned habitat similarly. Barred Owls used burned forests less than unburned areas, while Great Horned Owls preferred burned forests. Within burned forests, five owls used recent, severely burned areas equally with other types of burned forest patches. Only Northern Saw-whet Owls used low/moderate severity patches more than high-severity areas. At the fine-scale level, Flammulated Owls preferred burned forest patches with many standing snags, reflecting nest and perch availability. Great Grey Owls, Great Horned Owls, Northern Pygmy-owls, and Northern Saw-whet Owls responded to features corresponding with prey abundance and hunting strategies, such as tree density, coarse woody debris load, and shrub cover. Flammulated Owls, Northern Saw-whet Owls, and Western Screech-owls were absent from burned forests that had been fully salvage-logged. My results show that burned forests are viable habitat for owls, and should be managed to maintain resources linked to prey, nest, and roost availability. For several small owl species, retaining snags in post-fire forests promotes recolonization.