I was doing some research when I saw a little window open up on the bottom right corner of my screen, it was John asking if I had any papers on whether bath water for birds should be cold or warm. I did not pay attention to it because I figured I would find it either in FB, here or in my emails but I have not been able to find it since so I figured this was a good way of responding.
I had never actually done any type of research on this issue before because, to me, using cold or room temperature water was both common sense and part of my strict following of nature's ways but I took some time to look around and, of course, there is absolutely not a single avian scientific study on this [big surprise, right?]. Lots of opinions both ways but it seems to me that room temperature water in the winter is the way to go and I'll tell you why.
1. There is no warm water in the wild - even in the tropics, when it rains, the water is not really warm so, unless you believe that you, personally, know better than Mother Nature, I would say that cold or room temperature water is the way to go.
2. Taking into consideration that higher temperatures increase atoms kinetic energy [atoms move faster when warm or hot than when cold -think of water and how it reacts to heat or cold] and which makes warm or hot water better at dissolving [think of sugar in hot tea versus iced tea], it stands to reason that warm water would be more successful at dissolving oils than cold water.
3. Taking into consideration that pet parrots live in a human environment which is much drier than their natural habitats, I would say that further drying up their skin and feathers natural oils is not the best way to go.
Now, there are not studies on birds feathers and their reaction to cold or hot water [there are articles but are all about water birds which have particularly oily plumage meant to insulate the body from the cold water] but we all know that, when it comes to hair [made out of exactly the same protein as feathers], high temperatures can dry it up and make it frizzier than cold [the ubiquitous 'heat damage' in commercials]. Why? Because hot water 'opens up' the hair [this is actually most unscientific but it makes it easier to understand the actual effect], making it drier and more britttle [because it loses the natural oils that protect and moisturize it] which is HIGHLY undesirable in plumage!
From personal experience, I can tell you that I've had birds for over 50 years, never gave warm water to any bird for bathing and have never seen a single bird having a problem with this. PLUS, as I always state, to me, Mother Nature knows best so if there is no warm water in the wild for them to bathe and they all bathe very happily in their cold water, that's what my birds will get.
Last -and not meant as a snarky comment- one needs to always be in the lookout for the inevitable anthropomizing we all do with our pets, and warm baths for parrots fall right into this category. Parrots are not domesticated animals and do not benefit from being treated as one. I don't use room water temperature for bathing my dogs, I use lukewarm, but dogs are different from parrots and not only because they've been domesicated for 40,000 years but also because we crated breeds that have coats that would never make it in the wild - sheesh, we even have dogs that have no hair at all! So, although I would never recommend a room temperature bath water for a dog, it would be the only thing I would recommend for an undomesticated species.