Kili & Truman are well adapted to the cold. They have thick down feathers that they molted in during the fall. So now when I take them outside on 40 degree days, they aren't bothered by the cold.
You see during the fall I would put the birds out in the outdoor aviary on progressively colder days. First the days were in the 70s, then 60s, 50s, and eventually 40s. Their bodies and feathers adapted to this. When the winter got colder and I stopped taking them out, the only other thing I did to keep them more winter ready was to keep the indoor temp a bit lower (high 60s) so that the change to outdoor temperature would be less substantial.
The down feathers on Kili & Truman's heads are much much ticker than Santina's. Especially for Truman, he spends a lot of time out in the aviary during the colder months. His feather density feels nearly double what is is during the summer. When I run my hands through his feathers, they feel almost twice as thick and this is because the down feathers underneath the plumage are much thicker than usual.
On the other hand, Santina had come from a rescue where the temperature was constant. Her down is not much thicker than in the summer. For her going outside was much colder.
In just 5 minutes outside in 50F and direct sunlight, Santina was already shivering and had to be taken back inside. Kili and Truman managed to spend an hour outside at the park freeflight in 40F weather and sunlight. The flying definitely helped keep them warmer but since they take turns to fly and the other bird sits, flying wasn't the biggest factor.
This is why aviary parrots can manage most above freezing temperatures but housebirds should not be taken outside in strongly contrasting temperatures. As a rule of thumb, 10F less than indoors is no problem at all. 20F less than indoors is usually ok if it's sunny, not windy, and not for a prolonged period of time. Less than that only if they are under your jacket (and briefly) or well acclimated to colder temperatures. Avoid taking baby, old, sick, or frail birds outside in colder temperatures. If the bird's feet or beak feel cold, it is definitely time to move it inside and you should generally try not to stay out long enough for it to get to that. More tips on taking parrots outside in winter here.
It is winter. It is cold. We value days of warmth more than ever and so do the birds. This has been an especially cold winter and opportunities to get the birds outside for some natural sunshine have been very limited. This is why the moment it is sunny and not so cold I jump on the opportunity to get them out!
Yesterday it was a warm 46 degrees Fahrenheit. So I took Santina out briefly and she had her first encounter with snow. Since Santina comes from a warm room and heated rescue, I did not venture to keep her outside for long. She is not adapted to the cold. Kili and Truman on the other hand sport really thick down coats. When I pet their feathers, I notice an unusually thick layer of poofy white down beneath. The reason is because in the fall I continue taking them outside in the cold and also drop my apartment temperature some. They become acclimated to lower temperatures so brief encounters with temps above freezing are not a problem.
Since yesterdays outing was not expected, the birds were already fed and the timing was bad so they didn't care to fly much. Today, I checked the weather and realized it would be warm again. So I skipped morning flight training at home and got them outside for some freeflight instead. They're not used to flying in such weather but they did a stellar job none the less. They have been training up for this moment and keeping their muscles in shape with 1-2 mile nightly training sessions at home.
Truman seemed really eager so I let him fly first. He did one flight recall off the bat but refused to do anymore. He went back on his leash while Kili showed him how it's really done. She zoomed all around the park like a flying ace. She had not forgotten a thing in the months since her last freeflight. Truman was burning with jealousy and when he got his turn flew better than ever before. He flew longer, further, and more reliably. They both did a stellar job on this cool, sunny, February winter day!
Winter is here but that doesn't mean your parrot's need for natural sunlight is any less. This article is about how to get your parrot the natural sunlight it requires for its health in the midst of winter. How cold is too cold for your parrot to go outside? And ways of transporting parrots in winter are all covered right here.
Parrots require natural sunlight for vitamin D and calcium production. Also, it seems to play a role on their plumage, health, and overall well being. I have heard that they're requirement is 15 minutes of direct sunlight a week and it seems about right to me. In the winter it is difficult to get any, but some is still better than none.
Daylight balanced full spectrum light bulbs are supposed to help but I have strong doubts about them. Neither my nor other parrots I have seen that were in proximity to these bulbs match the plumage of parrots that spend time outside (I'm comparing mine before and after I started taking them outdoors as well as other people's birds). I know someone that keeps multiple Senegal Parrots and uses the expensive daylight bulbs that are specifically meant to simulate sunlight, and yet none of her Senegal Parrots have the rich yellow in the eyes like Kili does. Furthermore Kili's eyes did not become like this for over two years until I began regularly taking her outside. Thus the bulbs are something you can try, but their effect is somewhere between barely helpful to none at all whatsoever. Actual sunlight is what is really needed (and luckily cheap to have).
So given the importance of sunlight, yet thwarted by the coldness of winter, it takes some effort to get sunlight for my birds to get them through these dark months. I wait for the warmer bright sunny days and when I encounter one, I take them outside during the warmest time (between noon and 2PM). If I'm lucky enough that temperatures are over 50F, I don't sweat it and just take them out on a normal outing. Since they have feathers and aren't out terribly long, this works out fine.
If the temperature is between 40F-50F, I take Kili & Truman out but more briefly. Usually in this kind of temperature I only take them out on extremely sunny days where it already feels 10 degrees warmer just standing in the sun. A good way to gauge that the weather is warm enough to be safe for your parrots, go out wearing just a sweatshirt or light jacket. If you have to wear a warm coat, it may be too cold or you'll be so warm that you don't realize when it's been too long out. If you are dressed for 55-65 degree weather, then you'll be more in line with how your parrots feel and when you get cold, you'll know it's time to take it in.
If things get more desperate where the weather stays below freezing for weeks, I'll take any chance to get the birds out above freezing. Between 35-45 degrees, I make sure that there is no wind and that it is super sunny. I'll wear a warm winter coat and only take one bird at a time. I zip my jacket only 2/3 of the way up and keep the bird tucked underneath. I have the bird's head stick out and orient myself so the sun beams down on its head. Since a lot of the sunlight absorption happens through the skin on the head and around the ceres, this is a way of getting some sunshine for the parrot without letting it get too cold. I stay out this way for about 15 minutes and then take the other bird out for some sunlight too. I only take one at a time because I don't want them fighting under my jacket. For temperatures between 45-55F, I'll usually let a bird sit on my shoulder or hand while tucking the other under my jacket and they take turns. This way they are exposed but get to warm back up again under my coat. They actually enjoy the warmth and it's a good means for teaching them to be cuddly toward being held.
Taking the parrots out on winter days that aren't sunny is pretty pointless because they'll just be cold and not get the most important part of getting them outside. However, it's still good to do this from time to time just to keep them used to wearing harnesses and being out if there are no sunny days available.
If there simply are not any days above freezing where you live, another thing to consider is taking your parrots on a short vacation some place warmer. Check forecasts for warmer regions near you (even if they aren't really warm but at least match above criteria). It will do your parrots a lot of good to have an interim burst of sunshine to get them through the remaining winter.
If you need to transport your parrot during the winter, it's a good idea to run your car for a while before bringing the parrot out to get it warm. Cover the parrot's carrier with a towel at home for 10-30 minutes beforehand so that the heat builds up inside the carrier to keep it warm. I actually place the carrier on top of a warm (but not hot) radiator with the cover to make it even warmer inside. Pull the car up as close as possible and bring the parrot in. Make similar arrangements on the destination end to keep the parrot outside as little as possible. Run the heat up hotter in the car prior to opening doors so that the temperature doesn't drop too much.
To recap, the lower the temperature, the more picky I am about the conditions outside and the shorter the time we spend out. I try to feel the temperature with the bird by not over dressing unless the bird is going to stay warm under my clothes too. I don't let warm winter days go by without taking the birds out because these are far and few. Finally if I can't find a single warm enough day in a very long time, I drive or fly south to some place warmer with them so they can get some sunlight to get them through the winter months.