Least Flycatcher - Empidonax minimus

Least Flycatcher undergoes a partial preformative molt and partial to incomplete prealternate molt. The preformative molt occurs mostly prior to fall migration; older birds may begin their prebasic molt on the breeding grounds but replace most of their feathers after migration. Because of this, FCF (HY), FCA (SY), and DCA (ASY) individuals may be distinguishable through fall migration, although FCA and DCA plumages can be difficult to reliably distinguish, warranting use of M-FCA (AHY) in many cases. Sexes are identical in plumage; breeding females have a brood patch, but males have a poorly developed cloacal protuberance and may be difficult to identify with confidence.

Least Flycatcher is similar to other small Empidonax flycatchers (especially Dusky and Hammond's) and should be identified with caution especially where ranges overlap.

Quick tips

• Look at the wing bars, which are buffy on FCF (HY) individuals, mixed white/buffy on FCA (SY) individuals, a more subtle contrast between whitish and yellowish on DCA (ASY) individuals, and uniformly whitish on DCB (AHY) individuals.
• Examine the rectrices, which are narrow and pointed on FCF (HY) and some FCA (SY) birds, mixed pointed and rounded on some FCA (SY) birds, and uniformly rounded on DCA (ASY) and some FCA (SY) birds.

Species account prepared by McGill Bird Observatory (2018). Last updated by Marcel Gahbauer (Mar 2022)