My Amazon's recently started some odd behavior. When he eats he's started to bob his head and make a ton of noise, it's not squawking, it's kind of a sing-songy mumbling. After a bit of bobbing his head it seems like he vomits, but I'm not sure, and if he does it stays in his beak and he just swallows it. After (and sometimes during) he goes right back to his food. I can't find out anywhere what this is. Should I take him to the vet?