Wednesday, 16 April 2025

Presenter: Toby St Clair

Coastal Western Screech-owl (Megascops kennicottii kennicottii – WESOke) records have declined dramatically throughout the Pacific Northwest over the past 20 years. We conducted a series of nocturnal surveys to improve understanding of WESOke population trends, habitat associations, and the impacts of invasive Barred Owls (Strix varia) and landcover change (e.g., forestry) on WESOke occupancy and detection rates. Surveys were conducted using standardized call-playback methods and bioacoustics recordings using Autonomous Recording Units (ARUs) around the south coast region of British Columbia (BC) and on Vancouver Island, BC during February through April of 2021 thru 2023. Preliminary results suggest few WESOke remain within the valley-bottom, riparian habitats where the majority of historical WESOke records in BC have been documented. However, we regularly detected WESOke within old-growth (250+ year old) forests, including cedar dominated forests on Vancouver Island. Our and others’ results suggest WESOke populations are persisting at relatively high occupancy rates (>50% of potential territories) within previously understudied habitats including low productivity bogs (e.g., on northern Vancouver Island in the Nahwitti Bog) and high productivity cedar forests (e.g., on the west coast of Vancouver Island in Carmanah Walbran Provincial Park and adjacent forests that, for now, remain unlogged). Populations of WESOke within these habitats appear resilient to increasing densities of barred owl in the region. We hypothesize that aspects of habitat types in which WESOke persist reduce the availability and/or abundance of Barred owl prey, but maintain either smaller prey suitable for WESOke or thicker understory vegetation more accessible to WESOke and that provide cover/security for WESOke and Barred owl prey. Occupancy analyses are recommended to test this hypothesis using survey data collected with Pacific Megascops Research Alliance protocols since 2021 throughout coastal BC and historical datasets these protocols were designed to align with.

Toby St. Clair is a wildlife biologist focused on improving our understanding of biological systems to enable a more sustainable relationship between people and the
environment. He has conducted a wide range of studies in coastal and terrestrial ecosystems in academia, for NGOs, as a consultant, and as a volunteer. Since 2021, as co-leader of volunteer-driven Pacific Megascops Research Alliance (PMRA), Toby has been applying his knowledge of experimental design and nocturnal systems to dig into the ecology of coastal Western Screech-Owls (WESOke). With other researchers at PMRA, Toby aims to improve understanding of factors that have driven declines of this historically abundant species which has disappeared from much of the Pacific Northwest over the past 20 years.  At PMRA, Toby is also working to inform conservation and habitat management for WESOke in BC.