Gezellige_Poes
Songster
Agree with @cavemanrich that this little peep is severely malnourished and the fact that he is so eager to eat is a really good sign. I would not be so quick to diagnose him or pump him full of all kinds of chemicals. He needs good food and rest. You rescued him just in time by the looks of his breast bone. I would also make sure he has access to some fine grit or mix it in with his food. A cuttlebone is good, too. You may try to offer him a baby food mash, such as this: https://www.amazon.com/dp/B0002DGJH8.CCsGarden
Looks like the pigeon is super malnutrition. Keep feeding him BEST YOU CANIf he is eating,, that is a good sign.
I cant help you with canker, or such. Never encountered it.
@RoostersAreAwesome Please explain why you think this bird has canker and what this is.