What's the temperature in your home when the heat isn't on? Chances are, if he's dunking himself the temp probably isn't an issue for him.
Drafts can be tough for our birds, but that's because of how birds regulate their own temp. Having dramatic shifts like what happens with drafts can get them sick. But so long as there isn't a draft, you might be worrying overmuch in this instance.
Also, he might be letting you in on a little secret. He may actually prefer cooler water. Their preferences aren't only tied to pressure. They can also be tied to temperature as well. For example, Jolly definitely prefers his water on the cooler side. Maya, however, prefers her water significantly warmer. It's a matter of individual taste.
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