Small, handsome swallow of boulder-strewn rivers. Black-and-white pattern is distinctive but can be surprisingly hard to discern in bright sunlight. Note long-tailed profile and habitat. When gliding, often appears to hold wings below the horizontal. Seldom if ever encountered away from rocky rapids, around which groups cluster, sitting directly on rocks and flying about, chasing insects. Tends not to fly higher than treetop level. Often found with the more widespread White-banded Swallow.