Flying south to escape cold northern winters is a luxury for the birds, right?
Not always.
Hey guys, Amy here with DNews, and as you suffer through the dregs of a ridiculously
cold winter you’re not alone.
Some species of birds are right there with you, but without the benefit of indoor heating
and wool sweaters.
So how exactly do small animals survive harsh winters?
Whether or not a given bird species flies south for the winter depends a lot on what
its diet is.
If a bird exists largely on flying insects and nectar it will likely migrate south during
the cold seasons since these food sources aren’t exactly plentiful in cold weather.
But if a bird lives off seeds or insects that live under tree bark, it can usually find
enough food to spend the winters in the north, even if the temperatures drop dramatically.
But having food doesn’t equal warmth.
Small animals have a large surface area compared to their body size.
They also can’t store as much fat so they have less insulation.
All this means they are more prone to losing heat once the cold sets in, and surviving
a cold winter is all about preventing heat loss.
Biologists at the Norwegian University of Science and Technology did some research on
the survival skills of these non-migrating birds and found some interesting things.
For instance, some species survive by using the snow to their advantage.
Like the small hazel grouse or hazel hen common in Northern Europe as well as small rodents
like voles and field mice.
These small animals burrow into the snow, digging out little tunnels to sleep in at
night or rest in during the day.
The snow’s insulting properties mean these animals can focus on finding food and not
on surviving cold nights.
For some species, strength comes in numbers.
One of Norway’s smallest birds, the Eurasian wren, spends cold nights huddled together
under the snow.
They can congregate into groups of as many as 60 birds, huddling in layers to share and
conserve vital body heat.
But it’s not the case that all species make their own nests to fight off the cold.
Some species of tits just take over existing nests, often fighting over the best sleeping
spots at twilight.
And some birds have a completely different way of dealing with the cold: they can actually
slow their metabolism and lower their core temperature to reduce body heat loss.
Like willow tits.
These tiny birds can reduce their body temperature from about 105 to 87 degrees Fahrenheit.
They have a finely tuned internal thermostat that tells the bird to start shivering when
its core temperature reaches about 90 degrees.
Just the act of shivering produces enough heat to allow the bird to stabilize its core
temperature.
Aren’t you glad you don’t have to tough it out outside all winter?
But if you ever have spent a recreation night out in the cold, how did you stay warm?
Let us know in the comments below or you can let me know directly on Twitter as @astVintageSpace.
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