Insights Into the Ecology of a Widespread but Poorly Known Aerial Insectivore and a Theoretical Basis for Range Expansion Following Repeated Vagrancy Events

Over the course of the last two centuries, Northern Rough-winged Swallows (Stelgidopteryx serripennis) have expanded their range across the North American continent but have remained a relatively poorly known species. In this paper, I discuss two aspects of their nature history that has received little attention. First, I document an instance of Northern Rough-winged Swallows digging their own burrow, which was for the better part of the last century considered a behavior that was either lost or never occurred in the first place. Second, I review the natural history literature to document qualitative patterns evident in their expansion over the last two centuries. In doing so, I define three potentially useful concepts that can he applied to understand species' range shifts: an Expansion Chronology, which is a spatiotemporal map of a range shift; the concept of Vagrancy-induced Range Expansion, where a species undergoes repeated movements outside of their typical geographic range (defined as vagrancy events), leading to the regular occurrence in a new region (e.g., regular overwintering or nonbreeding occurrences); and the concept of Vagrancy-induced Long-distance Dispersal, which is specifically expansion of a species' breeding range following repeated vagrancy events.