Food Availability and its Influence on the Sustainability of Migratory Bird Populations on the Inspiration Ridge Preserve in Homer, Alaska

Abstract

Tree swallows (Tachycineta bicolor) and violet-green swallows (Tachycineta thalassina) are migratory songbirds that travel to high latitudes to reproduce and raise young over the summer. Their migratory timeline includes migrating to North America, where they leave their wintering grounds in Central and South America in March and reach northern regions mid-late May. They will then breed and raise their young until late July and then migrate back to southern regions for the winter. Tree swallows and violet-green swallows, along with many other migratory birds, are predicted to see declines as climate change progresses due to timing mismatches between their arrival at a nest site and emergence of their prey. Anecdotal reports in Homer, Alaska suggest that climate change is already affecting swallow abundance. The Center for Alaskan Coastal Studies deployed nest boxes for use by tree and violet-green swallows on their Inspiration Ridge Preserve property outside of Homer, Alaska to aid swallow conservation efforts. Our University of Michigan School for Environment and Sustainability Master’s Project group traveled to Homer, Alaska to work with CACS and monitor nest box use by tree and violet-green swallows and estimate invertebrate prey abundance and composition during summer 2023. Our work included conducting songbird, terrestrial arthropod and benthic macroinvertebrate surveys, nest box monitoring, and the development of a citizen science plan to involve youth in conservation efforts. We found low nest box use by tree swallows on Inspiration Ridge Preserve, and no correlations between nest box use and surrounding environmental factors. Additionally, in our benthic macroinvertebrate surveys, we found that all ponds on the property scored ‘excellent’ or ‘good’ for water quality. Our terrestrial arthropod surveys found a wide range of species present, but the community was dominated by springtails (Collembola spp.). Finally, we found a diverse community of birds present on the Inspiration Ridge Preserve, with 39 different species represented during surveys. We recommend further monitoring of nest box use by tree swallows and further development and implementation of the citizen science guidelines outlined in this article.