Honestly, I have never heard another bird that sounds like a HOWR. Their song is quite unique. My guess would be that you have a HOWR somewhere nearby. They are quite loud for such tiny birds.

Kendra, that was my thought too, I mean I know they are around, they just don't come out of the woods (unless they are disturbed). These birds sound like they are right up in the trees next to my boxes. I look and look with my binocs but never see anything that even comes close to looking like a HOWR. (I do put up Wren guards). I just think it's odd that if they are out in the open like that, that they are not filling my boxes. Whatbird.com has the recorded call, also does not have a "similar" listed. Going on 8 years and only the one year did I ever have HOWR but I hear this call every year. HHUUUMMM scratching head....