You could always try to put an egg down and then sprinkle about 2 feet around it with flour. You may be able to identify the robber by his foot prints.
Helped me figure out who our egg robber was when I couldn't trap it. Figured out it was a coon (a big nasty boy too). Changed the bait to a bowl of pepsi and caught him that night. There are a bunch of websites that help you figure out tracks.
http://www.tahoma.wednet.edu/subsite/ths/teachers/szkweb2004/apweb2005/envirothon/pdfs/Track1.pdf
or
http://www.bsatroop542.org/animalid.htm
Good luck...
Helped me figure out who our egg robber was when I couldn't trap it. Figured out it was a coon (a big nasty boy too). Changed the bait to a bowl of pepsi and caught him that night. There are a bunch of websites that help you figure out tracks.
http://www.tahoma.wednet.edu/subsite/ths/teachers/szkweb2004/apweb2005/envirothon/pdfs/Track1.pdf
or
http://www.bsatroop542.org/animalid.htm
Good luck...