Do birds shiver?


It takes a lot of nerve to be a bird that chooses to call Minnesota home for the winter.

Imagine being just a few ounces of fluff poised on a branch with below-zero temperatures threatening your livelihood. Options would seem limited to a wild bird.

But as Minnesota DNR nongame specialist Christine Herwig explained at a recent birding event in New York Mills, the birds we spy this frigid time of year, for the most part, migrate here—as if this is some kind of winter vacationland.

Herwig first became interested in birding in college and remembers a certain trip she made out east with her dad that really impacted her.

She was going out in search of birds with her dad and remembers hearing a sound as if it were raining on the clear day. She looked up above her and there were song birds flitting from branch to branch opening up birch catkins. The seeds were raining down upon the forest floor.

"It was a magical moment," she remembered.

She has since devoted a great deal of time to understanding Minnesota's birds and sharing information with those who want to catch a glimpse of one of the feathered creatures.

Herwig's main goal was to explain how Minnesota's birds survive on their own and how bird enthusiasts can provide food and habitat to have these birds in their backyard.

Birds modify their feeding

Because our landscape changes dramatically in the winter, so do the eating habits for area birds. Watch for birds to feed on the side of trees out of the wind. Birds feed on high energy/high fat foods this time of year.

To better accommodate the birds, Herwig mentioned placing some sort of roof over the feeding stations to keep snow off the feed. Placing multiple feeders in various places not only limits bird competition, but it also can provide various directions to feed out of the wind.

As 7-year-old Joanna Dardis and her mother Ann of Perham learned, bird food full of millet is more of a summer blend, birds don't want that in winter. Joanna's mother said they recently got into bird identifying as part of their homeschooling curriculum and part of the materials included the millet-filled bird food, which the birds have not touched yet.

If you only buy one type of food, go for black oil sunflower seeds, Herwig said. But to bring in more varieties, add in some nuts and hang some suet. Those are all high-fat foods that give the birds the energy they need.

Birds modify their bodies

Birds can add on about 20 percent of their weight in feathers, meaning about half the birds weight can be in their feathers in the winter.

Birds can even constrict their blood flow. "In extreme conditions, they can constrict blood flow to only their major organs," Herwig said. "With restricted blood flow ... they just let less blood move to extremities when not in active use. Doing so means less energy to circulate blood and less warmth that is lost."

And birds can turn their legs into heat exchange stations.

With countercurrent heat exchange, the warm blood leaving the body is cooled before it reaches the extremity (like a foot). Similarly, cool blood is warmed before entering the body. The heat exchange occurs because their veins and arteries are located near each other so the heat is transferred.

"By cooling the blood before it reaches the foot, they do not lose as much heat, which is really energy loss, and they likely do not feel as cold because there is less of a temperature difference between the environment and the foot," Herwig said.

And by warming the blood before it enters the body, they are less likely to get chilled by the cold blood, she added.

Birds body temperature in summer runs around 106 degrees, but when the temperature drops, a bird can drop their body temperature 20-50 degrees in order to use less energy.

Speaking of energy, birds need to consume about 35 percent of their body weight in food every day to fulfill their energy requirements.

"Birds do shiver, but it's different than us," Herwig said.

It's not the visual shivering that we are used to, it's more of a contracting of muscles that fluff out the down of the birds. And not unlike us, "it takes a lot of energy."

Birds modify their shelters

Some birds like grouse head for the subnivean zone, under the snow, to avoid the cold. It's been found that when temperatures dip down to as low as 40 below zero, it can remain at 20-30 degrees above zero under just six inches of snow, Herwig said.

Birds and mammals hang around evergreens in the winter because they are excellent at blocking wind and soaking and holding heat because of their dark color. Birds also like dead trees for making cavities in, and brush piles for escaping the elements.

If you have the option of doing so, keeping some dead trees and brush piles around your property is a good idea for bird and small mammals to live in, according to Herwig.

Be a birder

The presentation in New York Mills was organized by the Little Big Year group. The Little Big Year is a bird sighting program designed for anyone interested in birding, whether novice or expert—no matter your age or where you live in Minnesota. The group participates in various birding activities over the course of the year. The group also competes to see who can identify the most birds in the state of Minnesota each year. Cost to join is $10 except those under age 16 can join for free. Find out more at

For more information, contact Alice Martin at 218-385-3245.

Martin, a resident of New York Mills and leader of the Little Big Year group, said she began as a closet birder in 1999 and has since traveled the state adding to her growing list of bird species.


Winter birds

While you may encounter other varieties, Herwig mentioned several winter birds to identify this season. See how many you can spot from the comfort of your picture window or out on the forests and prairies around this diverse state.

Chickadees - one of the smallest birds to stay through Minnesota winter. Distinctive black cap.

Snowy owl- Minnesota's heaviest owl. White with dark flecks helps it blend into the ground where is nests. Look for this bird in open areas.

Great gray owl - Look for a white beard and yellow eyes. Minnesota's tallest owl.

Northern hawk owl- When perched, this owl looks like a hawk.

Northern shrike - This predatory bird is about the size of a robin and is known to impale its prey (mice, insects, snakes) on thorns or barbed wire fences.

Redpolls (common or hoary) - This is the smallest of Minnesota's winter birds. They can increase plumage by 35 percent during the winter. They eat 42 percent of their body weight daily during the coldest days. They even have a pouch inside their mouth that lets them store food for later. The common redpoll has more red, while the hoary is more white in color.

Pine and evening grosbeaks - These birds have heavy bills for cracking seeds. They are commonly seen at feeders.

Bohemian waxwing - Nomadic birds that travel in search of fruit. Fruit has less fat content so they need to keep moving to keep eating. If you find them, you'll likely just hear the sounds of eating and flitting from branch to branch as they have no song.

Snow bunting - Look for these birds at road sides foraging for seeds. They are mostly white with dark markings on back and wings.

Lapland longspur- These have a long claw out the back of their foot. Look for a rusty patch on the wing as well the back of their necks. Mostly black face, sparrow-like bird.