Prior to this winter storm, migration in Manitoba was preceding as normal with people reporting birds like Canada Geese, Dark-eyed Juncos, American Robins, Trumpeter Swans, Herring Gulls and more. While these birds are likely not enjoying the spring snowfall (similar to us humans!), they are adapted to withstand the occasional bout of cold and snowy weather. Similar to humans and other mammals, bird need to keep a constant body temperature, regardless of the weather.
All of the birds I listed above are early spring migrants to Manitoba. With our unpredictable spring weather, this means that they have evolved to be successful under a variety of spring conditions – from warm weather to cold weather, rain to snow!
Feathers are a bird’s multi-tool – they serve many different purposed! A bird’s plumage can help attract a mate, or provide camouflage. However, one of the most important roles of feathers is to help keep a bird warm and dry. During periods of cold weather, a bird will fluff up their feathers in the cold to trap as much of their body heat as possible. In fact, they can seem up to 2-3 times their body size all fluffed up! This is similar to how a down duvet traps your body heat. The average bird’s body temperature is approximately 40.6oC (105oF) and they can maintain that in cold weather. Additionally, the oil that birds apply to their feathers while preening works to help repel moisture.
Juncos are a more ball-shaped bird in general but you can see the difference in the body shape of a cold junco! Photos from eBird.org (left) and audubon.org (right).
Birds can shiver to help maintain their body temperature in cold weather. When birds shiver in cold weather they activate opposing muscle groups that contract against each other. This allows the birds to better retain body heat.
Bird feet in general can withstand lower temperature as they are mostly tendon and bone with little nerve or muscle tissue, so there is not much to freeze. However, the feet of ducks, geese, and gulls have evolved further to withstand cold water and ice. This is done through an adaptation called counter-current heat exchange in their legs and feet. Warm, oxygenated blood is pumped from the heart into the feet through arteries, which are close by the veins in the legs and feet that are returning colder, deoxygenated blood from the feet back to the body. As the arteries and veins are close together heat is transfer from the warmer arteries to the colder veins. Counter-current heat exchange allows the core body temperature to stay warmer, rather than losing heat through the cold legs and feet. Other mammals that live in cold climates, such as squirrels also use counter-current heat exchange.
There are a number of different ways that birds can alter their behavior to stay warm during spring cold spells. As humans, we can often feel the warmth of the sun in the spring, even if the air or wind is a bit chilly. Birds (especially dark coloured birds) can warm up on sunny days, by doing the aptly named “sunning” whereby they turn their backs to the sun, exposing the largest area of the body to the sun’s heat.
Birds can also flock together to help keep each other warm with combined body heat. In addition to the flocking itself birds may also gather in areas sheltered from the wind or cold, such as in sheltered shrubs or cavities in trees.
We talked about feathers above, but what about areas on a bird’s body that do not have any feathers? The feet, legs and bills/ beaks of most birds are not feathered. These areas of the body are kept warm by tucking them under areas that do have feathers. Birds may stand on one foot, with the other tucked up under the body feathers, or sitting on their feet which allows them to cover both legs and feet with their feathers. Similarly, they may tuck their beak/bills into their shoulder feathers to breathe air warmed by their body.
It can take a lot of energy to keep warm, so food sources during early spring cold snaps can be especially important. In urban areas, as well as rural farm yards, birds can often find supplemental food through bird feeders. High energy foods that are safe for a variety of birds include black oil sunflower seeds and suet.
The next few days might just be the perfect time to observe how birds adapt to the snowy conditions from the comfort and safety of home!