Using a good cloth cage cover at night helps a lot, LH. Our big old house in CT was really chilly and drafty, esp. in the winter when it was also damp. I'd say at night it probably was around 66-68, the same in WY. I don't think below that, for very long, would be good for them. The main thing, from my experience, is to keep them out of drafts. One product I found VERY helpful, when my birds showed symptoms of bacterial infections MARVEL AID.

href=http://birds.about.com/od/breedsofbirds/a/choosingabird.htm>HERE is some good information.