Everyone's butt is warm whether it is a bird, dog, cat or human.
If your bird feels feverish, then he needs to be seen immediately by an Avian Vet in your area. Excessive body heat indicates a fever may be present, so please do not wait around for him to die from an untreated physical issue.
Thanks for writing and let us know what Avian Vet has to say and how your bird is doing,