Weiss: How do birds survive and adapt in cold weather?
A recent trip to Colvill Park in Red Wing left Post-Bulletin Outdoors columnist John Weiss wondering how birds handle the bitterly cold Minnesota winters.
RED WING, Minn. — Fog swiveled and curtsied over the Mississippi River at Colvill Park in late January as my wife, Debbie, and I watched grand, majestic bald eagles circle and shriek, dive and pull up, rest in trees.
Oh yes, large flocks of mallards and goldeneyes paddled in the water, but, while attractive, they are no match for eagles.
Then I noticed something odd and so did Debbie: A few mallards had something silver in their mouths. Surely mallards weren’t eating fish, because everyone knows they eat only plants. I took pictures, blew them up in my viewfinder — fish they were in their beaks, gizzard shad to be exact.
Forget the eagles, we watched the mallards.
“I enjoyed a lot watching the ducks catch the fish and sometimes even another duck chasing another duck for a fish,” she said. “I could see them try to get something they could swallow, something they were struggling with … I have never seen a duck do that.”
Andrew Limmer has.
The southern Minnesota regional director for Ducks Unlimited said when he lived in Milwaukee, he’d see mallards eat fish on Lake Michigan.
“Mallards are known as opportunists,” he said. “Fish are not at the top of their choices” but in winter they will eat fish. “This time of year, (for) the ones that decide to stick around here, food sources are limited."
At times, mallards, which are a puddle duck, will even dive a little, he said.
Goldeneyes we saw with the mallards also ate fish but that’s more common for the diver duck, he said. “They will certainly go after fish along with snails,” he said.
So that got me wondering — if mallards change behavior in winter, how about other birds? I had never really thought about it. I knew groundhogs, reptiles and amphibians hibernate (bears just go into torpor) while deer add a lot of fat as well as an extra layer of hair for insulation.
Birds? I wonder.
Clarissa Schrooten, a naturalist at Oxbow Park and the Zollman Zoo, north of Byron not only wonders but has also done research and what she found was rather stunning. “It’s wild, it really is wild how nature is so adapted for animals to take on weather that is changing, and so cold and even brutal to our standards,” she said.
Here are a few ways they adapt:
- Birds living farther north grow bigger (just like deer, fox and moose) so they have less skin in relation to body weight - they lose less heat. Bald eagles we watched late last month weigh 8 to 10 pounds while Alaskan birds are around 12 pounds “to make themselves hardy so they can endure the cold,” she said.
- Blackcapped chickadees, these cute little birds so common at feeders, have an even wilder way - they add brain capacity. “They can increase their hippocampus and that is their part of the brain that does memory.” They add about 30 percent by getting rid of unneeded cells so they are better able to remember where they stashed seeds.
- Birds are able to tolerate cold on their feet with countercurrent circulation that intertwines arteries and veins so blood has a more even temperature. Feet are warmer and the blood going from feet to heart isn’t so cold that it shocks the heart. That allows geese to stand on ice and not freeze their feet. They will also stand on one foot for a while to warm the other foot.
- Grouse add pectinations to their toes, which is a fancy way of saying they add growths to the side of toes to give them snowshoes for walking over snow and gripping icy branches. They also grow special feathers to cover their beaks to warm air before it hits the trachea.
- Goldfinches double the number of feathers from about 1,000 to 2,000 in winter. They also change colors for winter because they eat off the ground more and are less conspicuous against the snow. “They look like little dirt balls instead of being a sign saying ‘predators, come and get me,’” she said. Male cardinals, which feed more in trees, stay bright red.
- Snow buntings, which migrate here from up north, can drop body temperature 30 to 40 percent to tolerate cold without losing too much fat. At the same time, when they do that when sitting on nests (they can’t let eggs freeze) they are more vulnerable to predators. When hummingbirds are up here, they drop their metabolism in the cold so much that predators that prowl at night using thermal imaging can’t see them.
- Snow buntings and redpolls will tunnel into snowdrifts to get out of the wind. Redpolls also store seeds inside tunnels they make. “They have packed a lunch and they hang out” until it gets warmer, she said. Snow, incidentally, is an excellent insulator.
- Like humans, birds shiver to stimulate muscles to generate heat.
- Birds will change diets, looking less for plants and more for fats such as meat or fat in road kill or suet cakes. Some bluebirds will stay all winter if they can find a place to roost out of the cold. They either change their diet to more seeds or find insect eggs in bark.
John Weiss has written and reported about Outdoors topics for the Post Bulletin for 45 years. He is the author of the book "Backroads: The Best of the Best by Post-Bulletin Columnist John Weiss"