Bird-Built Snow Tunnels: Is it all 'Just Play'?

Do you remember those childhood Decembers when it snowed so hard that you had feet of packed powder to play with? You could build a snowman, have a snowball fight between snow forts, or - my personal favorite - you could tunnel. Now a researcher is suggesting that this is a favorite past-time for many small birds, too.

That's at least according to a study recently published in the Northeastern Naturalist, a BioOne scientific journal.

The study details observations made by Bernd Heinrich, a professor and biologist at the University of Vermont. The researcher headed out to Western Maine two years ago to watch a flock of about 150 redpolls (Carduelis flammea) make at least 252 cavities and short tunnels in the snow between November and the following February.

He recently admitted to New Scientist that he had always wondered why these birds, (or any small wintering bird for that matter) dug these tunnels and trenches. From initial observation it became clear that there often wasn't any additional food buried beneath the snow, so why the tunnels?

The researcher suspects, surprisingly, that the birds are simply enjoying their time in the snow.

"Play is defined as behavior with no immediate function, so in that sense, yes, it is 'just' play," he said.

Still, this playful behavior may have once had some serious roots, where groups of the birds farther north would be tunneling to make insulated pockets of warmth to spend the night in.

However, the playful redpolls in Maine don't huddle down in their tunnels like their northern cousins. That's because melting snow surface can freeze overnight, potentially trapping the birds in a chilly tomb.

However, the Maine birds will still tunnel during the day, and will do so with gusto if the rest of their flock joins in on the fun.

Heinrich observed that when one bird tunnels, all its friends and family will stop what they are doing to tunnel too, showing that it is likely just a social activity - bonding for birds during the holiday season.

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