Master of Science
Morbey, Yolanda E.
The post-breeding period poses significant threats to newly fledged birds due to predation, starvation, exposure to inclement weather, and collision risk prior to their first southward migration. I used automated radio telemetry to track 100 adult and 100 hatch-year Bank Swallows (Riparia riparia) in the Great Lakes ecoregion during the 2021 post-breeding period. Additionally, 74 hatch-year birds tracked in 2018 by Mitchell et al. were included. In 2021, daily apparent survival probability was higher for adults compared to hatch-years; we estimated that ~10% of hatch-year birds die within two weeks post-fledging but high rates of tag loss in adults and hatch-year birds precluded accurate estimation. Among hatch-year birds, there was some support that daily recapture probability was higher for those from natural lakeshore colonies compared to those from artificial aggregate pit colonies, but this could be due to inland locations of most aggregate pit colonies. Apparent survival among hatch-year birds was higher in 2018 than in 2021 and 2018 was also a drier year. Results suggest that colony type and age can affect survival and recapture during the post-breeding period.
Summary for Lay Audience
Groups of birds in Canada (guilds) have populations that are either increasing (e.g., birds of prey) or decreasing (e.g., aerial insectivores). Aerial insectivore populations may be decreasing due to a recent global decline in insect abundance, increased pesticides and environmental contaminant exposure through consumption of terrestrial and aquatic insects or climate change. In turn, these factors may lead to increased rates of mortality of young birds during the post-breeding period. The post-breeding period can be divided into two phases: parental dependence and independence. During the parental dependence phase, young birds are reliant on their parents for feeding and protection. During the independent phase, young birds must learn how to navigate unknown landscapes, gather food, and escape predation. Performing these actions can put young birds at a significant risk of failing to survive to their first migration. This mortality, in turn, can negatively affect the population sizes of aerial insectivores. One species in the aerial insectivore guild is the Bank Swallow (Riparia riparia). The Bank Swallow has been listed as Threatened in Schedule 1 of the Species at Risk Act (SARA) since 2017. Bank Swallows create burrows in vertical faces for nesting in two distinct areas: along natural lakeshore or in artificial human-made sand and gravel pits. My thesis aimed to estimate survival of adult and hatch-year Bank Swallows nesting in lakeshore colonies or pit colonies during the 2021 post-breeding period. Additionally, data from 2018 hatch-years provided by Dr. Greg Mitchell (Environment and Climate Change Canada) was used in this thesis. To estimate survival, birds were tracked using VHF (radio) tags. Radio tags can be detected by Motus towers to estimate movement and whether a bird has died. Results showed that lakeshore colony birds were detected by towers more than pit colony birds; this indicates a higher recapture and survival in lakeshore colony birds. Adult birds were found to have higher recapture and survival compared to hatch-year birds. One limitation to this study was tag loss/failure. Hatch-year and adult radio tags were found to prematurely fall off, limiting the length of time birds could be tracked. Future studies should address tag failure and aim to track birds up to and beyond fall migration.
Buchanan-Fraser, Christian M.M, "Post-breeding survival of adult and hatch-year Bank Swallows (Riparia riparia) in the Great Lakes region: a radio telemetry study" (2023). Electronic Thesis and Dissertation Repository. 9351.
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