It’s a common question among backyard birders – where do the birds that don’t migrate south for the winter sleep during those frigid nights? Not only that, but how on earth do they manage to stay warm? The answers to these questions may surprise you.
First, where they sleep. It may sound like a cop-out, but it’s true – most birds will sleep anywhere they can that they think will keep them warm. Songbirds such as cardinals, finches, and blue jays will usually seek out patches of thick vegetation, such as brambles, briers, or grape vines. Other naturally-occurring shelters that these birds will use include conifers and ivy-covered walls. Other songbirds – like woodpeckers, wrens, nuthatches and titmice – will seek out cavity-like shelters similar to the ones that they nest in.
Yet these shelters alone will not do the trick of keeping a bird warm during the winter nights. Birds have thus developed several other biological mechanisms and behaviors that aid them in their quest for survival. For starters, birds have much higher metabolisms than do humans, and consequently have much higher internal body temperatures. It varies by the bird, but the average body temperature is around 105 degrees Fahrenheit. Even with this higher starting point, it is hard for birds to maintain their temperature, having a disproportionate large amount of surface area to heat up relative to their core volume that generates it. So how do they overcome this? First, foremost, and most obvious are their feathers. Feathers are a great source of insulation against the cold, and many birds even grow extra feathers in the winter to further provide warmth. Not only this, but the oil that covers the feathers also provides another source of insulation. As a last option, birds will also fluff their feathers out – doing this creates air pockets that provides still more insulation.
It’s not just the feathers, however. Birds’ legs and feet are covered with specialized scales that are able to minimize heat loss. Not only that, but birds have the ability to constrict blood flow to their limbs via their control over the temperatures over their legs and feet – which further minimizes the heat loss. It’s also not uncommon to see birds tucking their limbs and other uncovered body parts underneath their feathers to afford them the same insulation that the rest of their body is getting.
So the next time you see one of your beautiful backyard birds looking for a place to sleep on a winter’s evening, don’t assume that it’ll be the last time you see that bird alive. Odds are that, thanks to its survival mechanisms, you’ll see it flying around again the next day, eating your seed as usual.
– By Sean Peick (Guest Writer)