Looking at the photograph of the hole the birds were working, I'd guess that it either held overwintering squirrels, or was of great interest to them. The hole apparently shows either chewing or scratches along nearly its entire circumference, which could indicate that squirrels were coming into it (or leaving it) from all directions - scratching the bark surrounding the hole as they came and went. If only birds are using it, there are usually scratches only on the bottom edge where their feet would gradually remove the bark with their perching and comings and goings. Just one opinion... Cheers... Bob Bob Hinkle Solon, OH ______________________________________________________________________ Ohio-birds mailing list, a service of the Ohio Ornithological Society. Our thanks to Miami University for hosting this mailing list. Additional discussions can be found in our forums, at www.ohiobirds.org/forum/. You can join or leave the list, or change your options, at: http://listserv.muohio.edu/scripts/wa.exe?LIST=OHIO-BIRDS Send questions or comments about the list to: [log in to unmask]