We've been waiting for such a day for the entire winter: it's sunny, snowy and not very frosty. Lest it used to be either cold or gloomy, or I was out working... In general, birds are totally okay with the frost if they are strong and well-fed. It's all about temperature swings when you want to take a bird outside. If it's about 25 degrees above zero at home, and it's 10 degrees below zero outdoors, then the temperature range is 35 degrees, and birds don't wear clothes to make this drop more comfortable. In case you prep your bird for such temperature swings in advance and in a gradual way (just like we've made it with Yoll, who spend many hours outdoors on a regular basis), then the bird's organism adjusts to them and does not get sick. Untrained animals can easily catch a cold or get pneumonia.
As for Eva, she was a bit uncomfortable with the crows, but they left us alone within 10 minutes.