One of the most strikingly plumaged of Neotropical hirundines, the Black-collared Swallow is inextricably tied to rivers, especially in areas close to waterfalls and rapids, however small, provided there is swift-flowing water. The bird’s clean white underparts contrast strongly with the blue-black breast band, crown and upperparts, which become blacker over the wings and long, deeply forked, tail. Black-collared Swallow is most widespread over northernmost Amazonia, in eastern Colombia to the Guianas, and over northern Brazil, but also occurs, more locally across southern Amazonia, and even further south in northeastern Argentina, at the world-famous Iguazu Falls. The species is most typically encountered perching on rocks in the water or making fast, low sorties over the surface in search of insects , but it is also capable of making higher, slower flights, and even circling over forest occasionally. Some irregular and probably highly local movements are suspected in some areas, perhaps in response to changing water levels, but in general the Black-collared Swallow is probably largely resident. The species’ breeding biology is very poorly known and demands further study.