A large, powerful swift, usually seen flying above montane forests. Similar in size and shape to White-throated Needletail and can be difficult to distinguish in poor lighting. At close range, grayish (rather than white) throat patch and a smaller, duller pale patch on the back are distinctive. If seen with White-throated, appears marginally smaller and less bulky, with a shorter-winged silhouette. Voice a thin, descending twitter.