The reason for the grubby appearance of this young bird is not apparent , although it appears to have dirt on its beak ; feather staining looks like oil . It is fairly tame and had been stealing the Curlew food , no discolouring of plumage noticed on those occasions . A watch was kept to see if it came back so that it could be given a quick hose down . Days later, two kookaburras , both clean , turned up and caused our resident Curlews to protest loudly , charging at the interlopers , as they eat young birds, their latest chick having disappeared after a few days .