Make A Heated Bird Perch My Friend's Parakeet( Young) Is Always "puffy" Yet Seems Healthy Otherwise. Any Idea Why He Does This?

My friend's parakeet( young) is always "puffy" yet seems healthy otherwise. Any idea why he does this? - make a heated bird perch

I baby-sit her and say, birds should not sit with pen drive above. Also do not tighten the rod. No variety of other symptoms. Eat well. Continue to do after he is satisfied that no bird cold (heat lamp)