my tree swallow and bluebird swapped boxes this season, which blows my theory that they require slightly different designs.... which was my story last year......OK so
The cool thing is that they return to the same place, both bluebirds are banded from last season, BUT returning to the neighboring box of slightly different dimensions. I didn't realize that they return to the same place.
Etna, New Hampshire
Cape May Raptor Banding Project Inc.