Date of this Version
Brown and Page, "A Hybrid Cliff × Barn Swallow from Western Nebraska," from Nebraska Bird Review (March 2015) 83(1).
The Cliff Swallow (Petrochelidon pyrrhonota) and the Barn Swallow (Hirundo rustica) occupy sympatric breeding ranges across much of North America, often nesting at colony sites that contain both species. Mixed-species nesting aggregations typically occur in box-shaped concrete culverts underneath roads or railways. Cliff Swallows’ enclosed mud nests can be as close as 1 m to Barn Swallows’ open mud nests, and at such sites Cliff Swallows regularly usurp both inactive and active Barn Swallow nests. The close proximity of these two ecologically similar species leads to at least occasional social interaction among them, such as during combined alarm responses at predators. Another consequence may be extra-pair copulation between male Cliff Swallows and female Barn Swallows, leading to intergeneric hybridization.
On 12 June 2014, we visited a double-tunnel culvert underneath Interstate 80 about 8 km east-southeast of Roscoe, Keith Co, western Nebraska (41°06.438′N, 101°29.634′W). There were no active Cliff Swallow nests at the site on that date, and we estimated about 15 active Barn Swallow nests, all with eggs. Our attention was drawn to a bird’s vocalization that resembled a Cliff Swallow's alarm call. We observed a swallow with plumage characters clearly intermediate between those of Cliff and Barn Swallows while the bird flew among Barn Swallows during an alarm response at us as we stood in the culvert.