Traill's flycatcher was a supposed species of tyrant flycatcher in the genus Empidonax, called Empidonax traillii. It was named by John James Audubon after his good British friend Thomas Stewart Traill.[1]
It is now considered to be two distinct but closely related species, which are outwardly very similar but prefer differing habitats and replace each other geographically without significant hybridization: