Songbird Survival in Winter

cardinal sitting on snow-covered tree branch

Songbirds use a number of techniques to survive during the winter. (Photo credit: Jaki Good Miller/Getty Images)

When it’s extremely cold outside, you might bundle up in multiple layers, put on gloves and a hat, and wrap a scarf around your neck. But what do songbirds do to survive cold winter temperatures?

Many species of songbirds have adapted to cold winter temperatures by migrating to warmer locations during the autumn months. These overwintering habitats are typically found in tropical southern latitudes far from the breeding grounds where the birds spend their summer months. In these warmer habitats, migrating songbirds find plenty of food resources to last them through the winter. Following the spring thaw, the songbirds return to their northern habitats to breed, and start the cycle anew.

But not all songbirds migrate. Why do some birds migrate and other birds do not? And for those birds that stay, how do they survive harsh winter climates, where temperatures may soar well below freezing?

Within a population of migrating songbirds, there will always be a few individuals that do not leave their summer habitat when the rest of their cohorts do. Many of these individuals will not survive the winter, thus reinforcing the migratory behavior by removing their “non-migrating” genes from the population. However, some individuals may survive the winter, and over time, a non-migrating population may arise.

Birds have many physical adaptations that help them to survive in cold temperatures:

  • A bird’s feathers provide insulation from the cold. In the late fall, a number of bird species grow extra feathers as a result of a late-autumn molt. Feathers also have an oil coating that helps to insulate and waterproof the bird.
  • A bird’s legs and feet are covered in specialized scales that prevent heat loss. Birds are also able to control the temperature of their legs separately from their body. This is done by constricting the flow of blood to their legs and feet.
  • A bird’s fat reserves provide insulation and store extra energy used to increase body heat when necessary. Birds typically gorge on food prior to the onset of winter to increase their fat reserves. Migrating birds use their fat reserves to fuel their long-distance flights to their overwintering grounds.

Birds also have behavioral adaptations that help them to survive the cold winter months. You may have noticed that on extra-cold mornings, birds sitting in the branches of trees have a very “fluffed-up” appearance. When birds fluff out their feathers, they are creating air pockets that provide extra insulation from the cold. Birds may also stand with their backs to the sun, with their feathers slightly raised. This behavior helps to heat their skin and feathers more efficiently. Another behavior is to stand on a single leg or crouch atop both legs, so that they are tucked beneath their feathers. Such behaviors shield their exposed legs from the cold.

At night, many songbirds flock together, regardless of species type. The birds crowd together in tight groups, which helps them to conserve and share body heat. Additionally, some birds go into torpor at night, which is a state of reduced metabolism. While in torpor, a bird’s internal body temperature is maintained at a much lower level than when the bird is active. The downside of going into torpor is that the bird is less alert, and thus more prone to predation. In addition, it takes a fair amount of body heat to come out of torpor, and this requires an almost-immediate intake of food once the bird is active again.

Many songbirds that do not migrate have been greatly aided by changes in their natural habitats. For example, the construction of structures (such as the development of land into neighborhoods) increases the number of places were birds can roost and potentially find protection from the elements. Human intervention, such as maintaining bird feeders and bird houses, also helps songbirds to survive through the cold months of winter.

Three things that you can do to help songbirds overwintering where you live include:

  • Putting up bird feeders (preferably in an area out of the wind) and keeping them filled with high-fat seeds and nuts.
  • Providing birds with a container of liquid water (and monitoring the water to ensure it doesn’t freeze over).
  • Putting up bird houses or roosting boxes to provide shelter for the birds.

More to Explore
Winter Birds FAQs
Why Do Birds Migrate?
Migration Blues: When Birds Don’t Migrate South
Winter Bird Feeding

Comments

  1. Wow! Great article! I never knew about torpor. That must be where we got the word I had to learn for the SAT. I always thought that test was for the birds!!

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