The Marsh Wren [Cistothorus palustris] has been referred to as the “Long-billed Marsh Wren” and may very well represent two (or more) species.
According to the Cornell Lab of Ornithology, Eastern and Western populations of this skulking wren have very different songs, so different that they may actually be two separate species.
Marsh Wren preening
He’s adorable (of course)
Kroodsma makes a convincing case for their being two species in The Singing Life of Birds. But I guess a paper has yet to be published, which would be required for the AOU to take action.
I certainly wouldn’t complain about their being more wrens to see. Wrens have to have the most personality/gram of any bird!