Obscure and difficult to see or identify in thick willows of swamps, lake edges and riparian areas in the west, the distinctive voice, sung by both male and female, makes its presence obvious. The nest is placed near water on a small twig fork and made of grass, hair, plant down and feathers. Its diet is almost exclusively insects caught in the air, but in the fall a few seed are also eaten. In the southwest US, this species is considered endangered as its riparian habitats are quickly disappearing.
The four-digit banding code is WIFL.