And just like the coats people wear, birds tend to get puffier in winter. “A bird's body heat warms the air between its feathers,” Marra explains. “So birds fluff up in the cold to trap as much air in their feathers as possible.

What does it mean when birds puff up?

Birds fluff up their feathers to keep warm, and also when they relax for sleep ... and also when sick. A bird who sits puffed up much of the day is likely in trouble. Tail-bobbing when breathing. Birds who sit there puffed up, bobbing their tails, may be sick.

How do you know if your birds are too cold?

Cold birds often sit with their feathers fluffed up to retain body heat, and they don't move around much. This behavior also can be a sign of illness. So if increasing the temperature of your bird's environment doesn't return it back to its normal behavior fairly quickly, contact your avian veterinarian.