Heller, Erin L.; Kerr, Kevin C. R.; Dahlan, Nor F.; Dove, Carla J.; Walters, Eric L.
(2016)
Flycatchers in the genus Empidonax are among the most difficult avian taxonomic groups to identify to species. Observers often rely on calls or songs in the field or detailed morphometrics in the hand to identify species. ...