I have a little friend a Robin that has a problem with its mandible, he/she is doing ok, I am feeding it live mealworms and it is getting friendly if it sees me it comes and tells me it wants some food so it looks like I will be looking after this one for a while :)
Aww poor robin, looks like a deformed mandible at the base to me (where the bony plates start to form) but good to hear it can still manage to eat mealworms and well done for keeping it supplied Jim. If as Paul says it is canker it will need to drink very regularly and the plumage often starts to look damp particularly on the head area and the bird starts to look very fluffed up; other indicators are bits of food stuck to the bill. Good luck to this little bird and hope its only mis growth of the bony plates.