Slim, long-tailed swallow with pale underparts and dark blue upperparts. The gray rump is not conspicuous when perched but can be discerned in flight. Found in grassland and open savanna, usually near water. Frequently in small flocks. Notable for its unusual habit of nesting in rodent burrows! Similar to Common House Martin, but has a gray rather than white rump, and a longer, slimmer tail.