Southward Breeding Expansion of Tree Swallows in Alabama

Hannah C. Wright^1,2,*, John W. Price¹, John A. Trent¹, Eric C. Soehren¹, and Scott A. Rush²

¹Wehle Land Conservation Center, State Lands Division, Alabama Department of Conservation and Natural Resources, Midway, AL 36053. ²Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Mississippi State, MS 39762. *Corresponding author.

Southeastern Naturalist, Volume 18, Issue 4 (2019): 548–554

Abstract
Since first confirmation of nesting in 1987, there has been a steady southward expansion of breeding Tachycineta bicolor (Tree Swallow) in Alabama. Using 220 breeding season occurrence records, we performed a breakpoint analysis to quantify the breeding expansion rate of Tree Swallows in the state. Between 1988 and 2013, our models indicated Tree Swallows expanded ~130 km south at a mean rate of 5.2 km/year. Possible drivers of this southward expansion include increased artificial nest box availability, aerial insect declines in more northern historic ranges, changing climate, and altered land-management practices. Our findings indicate Tree Swallows are following a similar southward breeding expansion pattern to that exhibited by Hirundo rustica (Barn Swallow) and Petrochelidon pyrrhonota (Cliff Swallow) in recent decades.

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