Crustavian Barnagoose

Once upon a time, it was believed that the barnacle goose and goose barnacle were one and the same animal. The geese were never seen to actually breed, and the barnacles looked a bit like the geese, so it was assumed the barnacles were in fact baby geese. Supposedly, trees would produce gummy goslings and then drop into the sea, where the birds would grow and develop within their shells, eating only the tree's sap. Some religious folks would use this unusual birth as a loophole allowing the geese to be eaten when they normally would be forbidden.