"Poor birds," you're thinking. "They look so frail hunkered down against the blowing snow!"
Well, think again.
Birds have developed and evolved many special adaptations to survive brutal winter conditions.
The biggest thing they have going for them are feathers. Feathers have evolved into many forms and are marvels of engineering. They are strong, lightweight, and durable, as well as having amazing insulating capabilities. Birds have a preen gland at the base of their tail that they take oil from to treat their feathers, adding more insulation as well as waterproofing them.
Birds have the ability to contour their feathers. They can flatten or fluff-up their feathers, allowing them to create more airspace between them. This allows them a way to regulate temperature. The hotter they are, the flatter the feathers with no airspace; conversely, the colder they are, the fluffier they are as they puff up and trap air that acts as additional insulation between their feathers, their bodies and more feathers.
And when birds are sleeping at night, they tuck their beaks into the feathers on their shoulder or back, thereby reducing heat loss from their unfeathered beaks, as well as breathing in air that has been warmed in pockets trapped by their feathers.
This is an excerpt of the Weekly Bird Report. Audio of the full essay, on bird adaptations for cold weather, is posted above. Give it a listen.