Greetings All
I've had a number of occurrences similar to Steve S's (not including actual mimids, of course)
This year, I heard a Red-eyed Vireo doing splendid imitations of Eastern Wood-Pewee and Great Crested Flycatcher and back in Washington, on a couple occasions I've heard Cassin's Vireo doing a wonderful Purple Finch.
Chats are almost as good as starlings and mimics. I've heard them, recently, do superb Bobwhite, AT Flycatcher, and a couple other species (again, escaping my limited memory, but not theirs)
Cheers
Steven Mlodinow
Longmont CO