Large swallow of tropical lowlands; both sexes resemble female Purple Martin of North America. Fairly common in towns, villages, open and semi-open country with taller trees and other structures that provide nest cavities. Upperparts dark bluish overall (brighter on male), throat and breast dusky, belly whitish. Lacks pale forehead and pale hindcollar of female Purple Martin. Larger than rough-winged swallows, with a more deeply forked tail, blue cast to upperparts.