Arctic Warbler
Phylloscopus borealis
Male's song is a monotonous trill with little variation. (Two songs of two birds, Denali Highway, Alaska.)
Habitat: Breeds in dense willows along stream beds.
Blue-gray Gnatcatcher
Polioptila caerulea
The gnatcatcher's common call is a nasal, high-pitched beeee, which it makes frequently as it forages in trees and shrubs. Its call may be overlooked easily in a noisy environment. (Albany County, New York.)
Habitat: In the East the Blue-Gray Gnatcatcher breeds in swampy woods.