I keep my Gouldians in a sunroom, which is usually slightly cooler than room temperature all winter. I keep the temperature in there between 65'F (18'C) and 55'F (13'C), usually around 60'F (15.5'C). I know finches can adjust to cool temps but I don't think Gouldians enjoy (or especially thrive) like that. They are tropical and at least somewhat more delicate than other finches.
So what I do is use a ceramic heat lamp over one corner of the cage, which is on all the time except in the heat of summer. I think the extra heat really helps them stay healthy. I also have electric baseboard heat on the wall behind my cage. So, while my sunroom gets cooler, the immediate area next to my Gouldians is warmer and they have a hot spot (under the heat lamp) where they can always go. While this might not be necessary if your Gouldians are in the house (at "room temperature" all winter), we do tend to keep our homes cooler nowadays to save energy and I'll bet any Gouldians would like the extra heat in winter.
I would swear that this extra heat source has increased the survivorship of my Gouldians. Baby or moulting Gouldians can be especially delicate and I've lost none of my 15 babies this year. Note: a ceramic heat lamp puts out no light and you can find one in any pet shop that has reptile-related items.


