Am trying to figure out what is leaving a "pellet" of dried stuff on our deck .... butcher birds love to come and help themselves to our dog's food, as do possums (and rats) at night. But somebody is leaving a "pellet". It looks too big for a butcher bird to pass by pooping (and I thought birds only pooped liquid stuff). It's oval, about 1.5 cm long and 1cm fat, and is brown and fibrous. Any suggestions? Many thanks.