Decoupling pioneering traits from latitudinal patterns in a North American bird experiencing a southward range shift

Eco-geographic rules describe spatial patterns in biological trait variation and shed light on the drivers of such variation. In animals, a consensus is emerging that ‘pioneering’ traits may facilitate range shifts via a set of bold, aggressive, and stress-resilient traits. Many of these same traits are associated with more northern latitudes, and most range shifts in the northern hemisphere indicate northward movement. As a consequence, it is unclear whether pioneering traits are simply corollaries of existing latitudinal variation, or whether they override other well-trodden latitudinal patterning as a unique eco-geographic rule of phenotypic variation.
The tree swallow (Tachycineta bicolor) is a songbird undergoing a southward range shift in the eastern United States, in direct opposition of the poleward movement seen in most other native species’ range shifts. Because this organic range shift countervails the typical direction of movement, this case study provides for unique ecolog..., Study sites and environmental data
Methods were approved by Appalachian State University IACUC #13-15 and US Master Banding Permit #23563. All animals were handled in such a way to reduce stress and avoid physical harm. All adults were released in their home territory. We conducted fieldwork during May-June 2015. Historical sites included Saukville, Wisconsin (43.382 N, 88.023 W), Long Point, Ontario (42.623 N, 80.465 W), and Wolfville, Nova Scotia (45.107 N, 64.378 W). Expansion sites included Bloomington, Indiana (39.142 N, 86.602 W); Ames, Iowa (42.073 N, 93.635 W); Davidson, North Carolina (35.438 N, 80.697 W); and Boone, North Carolina (36.196 N, 81.783 W). We recorded GPS coordinates at each nestbox (Garmin GPSmap 78s).
Sites were categorized as either historical or expansion based on prior publications (Lee, 1993; Shutler et al., 2012), bolstered by personal communications with local researchers and data from the Bird Breeding Survey (BBS; 1967 to 2017)(Sauer et al., 2017). Histo..., Excel