Northern Rough-winged Swallows (Stelgidopteryx serripennis) - These are common swallows where I'm from in Central Arizona, so it was interesting to record them in Costa Rica, too - they sound pretty much the same!
Northern Rough-winged Swallows (Stelgidopteryx serripennis) reel in the Spring air above Tavasci Marsh [Arizona], calling as they fly - notice, as in most swallows, that they call most when the flock is the densest (a mechanism to help avoid collisions?).
