クリエリムジアマツバメ Streptoprocne rutila

Fairly common and widespread swift of foothills and highlands; also ranges regularly to lowlands. About the size of a Chimney Swift, but typically has a slightly notched tail. Slightly larger and longer winged than Vaux’s Swift with stronger flight and more prolonged gliding. Usually seen in flocks, often associating with swallows and other swifts. Looks black unless seen at close range, when dark rusty collar may be visible (immature birds lack collar). Also note the voice: a crackling, buzzy chatter that sounds like electricity passing through wires.