Alder Flycatchers of all ages undergo a nearly complete to complete molt during winter, therefore all in spring are identifiable only as AHY except for a few SY individuals that have retained juvenile feathers. Sexes are identical in plumage; breeding females have a brood patch, but males have a poorly developed cloacal protuberance and may be more difficult to identify with confidence.
Alder and Willow Flycatcher are nearly identical in appearance and are usually identified reliably only through vocalizations; collectively they are referred to as Traill's Flycatcher. The description provided likely applies also to eastern Willow Flycatcher, but not to western Willow Flycatcher.
Species account prepared by McGill Bird Observatory
|Age / Sex||Image sets|
|Hatch year / Unknown
Upperparts brownish, with buffy wing bars; rectrices narrow and pointed.
|After hatch year / Unknown
Upperparts greenish, with whitish wing bars; rectrices relatively broad and rounded.
|Age / Sex||Age / Sex class description|
|Second year / Unknown||Upperparts greenish, with whitish wing bars; one or more retained brownish and worn juvenile inner primaries or outer secondaries, contrasting with fresher greenish feathers on rest of wing.|
|Juvenile / Unknown||Upperparts brownish, with buffy wing bars; rectrices narrow and pointed.|