Though this winter has been quite mild, there have definitely been some chilly days! Many animals hibernate through cold weather, and larger mammals have a thick fur coat to keep them warm... but what about birds? How do they stay warm when the temperature drops?
In the photos at the right, you can see that the swallows have huddled together very tightly to share body heat and one of the finches has tucked it's heads into its shoulder feathers to keep it's face warm. These aren't the only strategies birds use during cold winter days though. These swallows and finches are doing several other things to keep themselves cozy:
In both photos, the tree swallows and finches look very fat, but this isn't due to eating too many seeds - they have all fluffed their feathers outwards to trap more pockets of warm air close to their bodies and slow heat loss.
Additionally, they have all tucked their legs in close to their bellies to reduce the amount of heat lost from those feather-less body parts. You can see the difference in perching posture from the fair weather photo on the left, where the finch has its legs well extended from its body. And although we can't tell specifically, it is also possible that birds in the winter photos above could go into torpor to conserve energy. (Don't remember what torpor is? Check out the torpor blog post here!).