Tree Swallow Range Expansion 111 



Linville in the Mountains of North Carolina in 1991. All North Carolina 

 nest sites are in artificial banks made by large earth-moving equipment. 

 Thus, it appears that current land use practices have provided 

 open foraging habitats, and various man-made structures and land 

 modifications have provided suitable artificial nest sites, thus allowing 

 various species of swallows to expand their breeding range in the 

 Southeast. 



CONCLUSIONS 



Like other species of swallows, the tree swallow has expanded 

 its range considerably since the late 1800s. Earliest records show the 

 species to be a peripheral breeding species in the southeastern United 

 States, and nesting records are sporadically distributed both geo- 

 graphically and temporally (Fig. 1). Range expansion appeared to be 

 gradual through the 1960s and then explosive from the 1970s to the 

 present as the birds populated the Piedmont of Maryland, Virginia, 

 and portions of North Carolina (Fig. 2). The species expansion in the 

 mountains, Mississippi basin, and Coastal Plain occurred at different 

 rates. Overall the species has spread south over 600 km in this century 

 with approximately 220 km (35%) of this expansion occurring in the 

 last decade. Although various factors such as land clearing were 

 obviously necessary for the range expansion to occur, the timing of 

 these changes in land use does not appear to correspond directly with 

 the expansion in range. 



Although land clearing probably benefited all species of swallows 

 nesting in the Southeast, the change of distribution is also related to 

 availability of nesting sites. Thus, the northern rough-winged swallow, 

 the species with the least demanding requirements for nesting sites, 

 was the first to expand its range. Barn swallows followed, expanding 

 into the Piedmont and Coastal Plain as wooden bridges were replaced 

 with concrete ones. Cliff swallows have nested in North Carolina 

 only since the 1960s, and their current distribution is discontinuous 

 and dependent on the large reservoirs constructed in the latter part of 

 this century. Tree swallows expanded their range with the re-introduction 

 of beavers and after their adoption of nest boxes. The bank swallow, 

 which has the most restricted distribution, relies on exposed banks 

 that are sporadically distributed and often not continuously available 

 because of erosion and invading plant communities. 



ACKNOWLEDGMENTS— \ thank various participants of the North 

 Carolina Breeding Bird Atlas program administered by the North Carolina 

 State Museum of Natural Sciences for participation in our field studies. 

 Herb Hendrickson, Julie Angerman-Stewart, Eloise Potter, Maurice 



