I know some people out there already know what one is but I wanted to clarify it for everyone. ( Sadly) I just figured this out recently. A Traill's flycatcher is the name used when someone finds a flycatcher that could be either a Willow or an Alder flycatcher. The only way to tell them apart is if you here it vocalize. For a very long time the Willow and the Alder Flycatcher were considered the same species. Because even if you got to hold each one in your hand you would not be able to tell the difference. Because there isn't one except for the voice. A bird's song is one of the most important tools to memorize. It helps in so many ways.
Posted by John Mark Simmons