How Do Birds Survive the Cold?

Wednesday, February 7, 2024

 Birds are small, light weight, balls of fluff with bare-skinned legs that appear to offer no protection from the cold, and they don't live in cozy nests or dens through the winter - so how exactly do they survive the cold? Birds have evolved and adapted over millions of years to withstand even the coldest of temperatures. By understanding how birds make it through the winter months, we can help boost their chances of seeing another warm, spring day. 

Northern Cardinal, female

Body temperature, specialized feathers, and fat reserves
Birds already have a bit of an advantage when it comes to keeping warm in the cold, as they have a very high metabolism rate, and in turn, a higher body temperature than humans. On average, a bird's body temperature sits at about 105 degrees Fahrenheit (40 degrees Celcius), whereas the average human body temperature is 98.6 degrees Fahrenheit (37 degrees Celcius). But because birds have a higher metabolism, it also means that their caloric requirements are extremely high in relation to their body size. To help conserve energy and maintain body heat efficiently, birds have a few special physical qualities:

  • Feathers & scales: Certain feather types on birds' bodies aid in insulation, such as semiplumes which help add some insulation under the contour feathers, and down feathers which are fluffy feathers that lie under contour feathers with semiplumes, and are responsible for forming a thick layer of insulation. Some birds will also grow in extra layers of feathers during the molting process in the fall. In addition to insulating feathers, birds have small "scales" on their feet and legs that reduce heat loss, and are even able to control the temperature of their legs and feet by constricting blood flow. 

  • Winter fat reserves: As with many animals, birds will eat a little extra through the fall in order to build up an extra layer of fat. This thin fatty layer helps to add extra protection from the cold in the winter months, and also acts as backup energy for those long nights and days when the weather is just too extreme to go out and feed as much as is needed. 

American Robin, fluffed to keep warm

Shivering, fluffing, and roosting
In addition to physical adaptations, birds have also developed behaviours that help them keep warm through cold weather. Some we are familiar with and take part in ourselves, such as sunning and shivering, but others are fairly unique to birds. 

  • Shivering: This is a behvaiour that we have in common with birds, but shivering isn't just something that our body does involuntarily when we're cold. Shivering is the body's way of raising the metabolic rate to aid in generating more body heat. Because this requires more calories to perform, it is only a short term solution in extreme cold. 

  • Fluffing: Fluffing looks exactly as the name implies, birds fluff their feathers up giving them a "puffed" appearance. If you feed birds in your backyard you have likely observed this behaviour while birds are perched in trees or at your feeders on cold days. Fluffing helps keep birds warm by creating air pockets within the feathers that act as added insulation.

  • Roosting: Many species will congregate in large groups when settling in for the night in the winter months, often in trees, shrubs, or man-made roosting boxes. Though most don't spend their days with one another, sticking together in these tight spaces overnight to conserve heat is what helps many birds survive. Even birds who don't roost communally are strategic in where they choose to sleep through the night, picking spots that hold residual heat from sunlight through the day.

Red-bellied Woodpecker feeding on high-calorie suet

How to help birds through the winter
  • Offer seasonally savvy foods & keep the feeders full: Seasonally savvy bird feeding can not only help you attract a wider variety of species to your yard, but can actually provide great health benefits to the birds. In the winter, many birds' diets switches from a mostly insectivorous diet, to an omnivorous one that consists of seeds from conifers, fruits including cedar berries, sumac, mountain ash, and more, as well as any foods (including insects) that they cached before winter. Seasonally savvy winter foods include ones that are high in calories, fats, and protein, to give birds the fuel they need to get them through the long, cold nights and days. Some of these foods include suet like SuperSuetBark Butter, mealworms, and caching foods like seeds and tree nuts found in our Winter SuperBlend that birds can store throughout their ranges to eat at a later time. 

  • Install a heated bird bath: In winter, birds rely on snow consumption and naturally open sources of water for hydration. Open water is harder to come by when the temperature gets below freezing, and snow takes a lot energy to convert to water, so having a reliable source of drinking water available can mean the difference between life or death for some birds when the weather gets particularly intolerable. Heated bird baths can be purchased as a single unit and are simple to attach to a pole system, deck railing, or on stand alone poles, and are kept just above freezing by an internal heater that is not exposed to the birds. Alternatively, heaters are available to add to existing baths that are large enough to accommodate them. Either are great options to ensure your backyard birds have a supply of fresh water all winter long. 

  • Offer protection from the cold: Winter is pretty, but it isn't always friendly to us or the birds. During inclement weather birds are more likely to seek out food & areas that are well-sheltered. To help with this you can add weather domes above your feeders which act as shields from rain, snow, freezing rain, and wind. Domes will not only help the birds to feel safe & secure, but they can also help keep your offerings dry which cuts down on seed spoilage. Having an abundance of bird-friendly habitat is also of the utmost importance during the winter. This can be in the form of native trees & shrubs growing around your yard, man-made brush piles of twigs & branches, or even upcycled Christmas trees. Once the holidays are over and your Christmas tree is no longer needed, just toss it in the yard for the birds to enjoy. 

Now that you know how birds keep warm, check out our previous blog all about how birds beat the heat!

Happy trails!
- Shayna

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