As we begin to see our first snowy days and the sun starts setting before you can even get home from work, you may find yourself thinking about joining the thousands of birds that make the formidable trek down to South America where they will overwinter in warmth until spring.
While the migrating birds will spend the season in much milder weather, many others will remain here with us.
Any Mainer can tell you that winters here are no easy task, even with all of our resources as humans. But what if you are a bird with no hat, no gloves and no wood stove?
These hardy birds avoid dangerous and energy-intensive migrations but must face the cold alongside us.
Birds have developed many ways to survive the season including physical adaptations, changing behavior, and adjusting their diets.
Black-capped chickadees provide a great example of some of the physical adaptations birds have developed to survive cold winters.
Chickadees, like many other birds, can be seen fluffing their feathers more often in winter, capturing as much air as possible close to their skin. The air is warmed through their body heat and trapped by their feathers.
A less well-known winter survival method chickadees utilize is conserving large amounts of hard-earned energy while they sleep through a process called regulated hypothermia. They slow their metabolism by lowering their body temperature overnight as much as 15°F less than their average daytime temperature.
Another adaptation chickadees share with many other birds is shivering. Birds will continuously flex their chest muscles to generate heat.
Chickadees can lose up to 60 percent of their body weight each day from shivering and have to work hard to forage enough food to replenish this weight.
If you ever wondered how Canada geese and other waterfowl can stand directly on ice without freezing, the adaptation you’re interested in is countercurrent exchange.
Birds keep their bodies warm by allowing their feet to almost freeze. Blood vessels and arteries going to and from birds’ feet are located very close together. Cold blood flowing through veins back to the body from the feet is warmed by arteries that bring blood down to the feet.
This method prevents the bird’s body from receiving cold blood back into it from the feet.
Additionally, birds’ feet don’t become frostbitten in these cold temperatures because they consist mostly of tendons and bone and very little soft tissue.
In addition to physical differences between the seasons, birds will often change their behavior to survive the winter.
In the spring and summer, most birds are quite territorial, competing for resources and breeding partners. In the winter, many birds are known to roost communally at night to share warmth.
You can easily spot this in crows but many other birds like brown creepers and nuthatches will gather close in tree cavities to exchange heat.
Birds like the American robin can also be seen changing their behavior regarding diet. In the summer this species forages mostly for insects. In the winter, bugs can be very hard to come by so robins will adjust by eating a diet of almost entirely fruit, provided by native plants such as winterberry shrubs.
This season, as you turn on the heat and get out your winter gear, take some time to reflect on Maine’s birds.
Winter is a great time for birdwatching and appreciating the rugged birds that remain alongside us all winter.
Consider providing high-energy resources for them like suet, peanuts and black oil sunflower seeds.
And maybe spend some time researching native plants to add to your garden that can help support these birds next winter.
Brianna Guy is a naturalist for Fields Pond Audubon Center in Holden.
