Thesis Defence: Are Riparian Areas Thermal Refugia for Western Screech-Owls?

Megan Buers, supervised by Dr. Karen Hodges, will defend their thesis titled “Are Riparian Areas Thermal Refugia for Western Screech-Owls?” in partial fulfillment of the requirements for the degree of Master of Science in Biology.

An abstract for Megan Buers’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.

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ABSTRACT

Global temperatures have risen dramatically in recent years, with the frequency and duration of extreme heat events expected to continue increasing. Thermal refugia could allow wildlife to escape extreme heat and adapt more readily to temperature shifts. Riparian areas have been shown to act as thermal refugia, offering the ability to escape the heat of the day. However, little research has focused on nocturnal wildlife, which may be particularly vulnerable given that nighttime temperatures are rising faster than daytime temperatures. This study examines how the Western Screech-owl, a nocturnal bird of prey threatened by habitat loss in Canada, responds behaviorally to climate fluctuations, particularly changes in temperature and humidity. I investigated whether these owls select nest sites in habitats that can buffer extreme temperatures by locating nest sites in south-central British Columbia and comparing their thermal buffering capacity (TBC) to random sites and other available cavities within the owls’ territories. Additionally, I trapped and tagged owls to observe whether they used these refugial habitats for roosting or foraging (n = 31). Using cameras and autonomous recording units, I monitored nests to assess prey delivery rates to nestlings, testing if increased temperatures affect parental investment. I applied generalized additive models (GAM) to determine whether owls were selecting for various features, and to test the relationship between prey delivery rates and climate. The findings revealed no significant preference for nest sites with enhanced temperature buffering, nor did the owls roost in cooler microclimates. However, the owls decreased prey deliveries to the nest when temperatures exceeded 30°C and were found foraging more often in riparian areas during high heat, favouring areas with taller shrubs and canopies, closer to rivers, and at lower elevations. This study provides a comprehensive look at the behavioral adaptations of Western Screech-owls to climate change.