Why Do Birds Fly South for the Winter?

In the northern states, just before the leaves start to fall, birds begin to flock and prepare for their annual migration south. Birds that we usually see alone or in small groups during summer months will gather with others of their kind, or often with those of other species. Water fowl will congregate and form that well-known V pattern in the sky as they journey to warmer climes. Robins vanish, not to return until the spring, reminding us that a long, cold winter is bearing down on us. As ominous as the dirge of some death knell, when the birds start to leave we know the sweet warmth of summer is but a memory.

But not all birds fly south. Some remain through the snow and the cold, and some species are even more abundant during the winter months. Why do some fly south while others stay put? Why do some appear to thrive in the snow? When our birds fly south, where do they go, what do they do, and how do they decide when it’s time to come back? And how the heck do they know where they are going? These are some of the things I ponder each winter as I watch the little Black-capped Chickadees dart around my birdfeeder, and wonder where the Eastern Towhees have gone. So let’s find out!

At first you may think the reason birds fly south for the winter might have something to do with the warmth of the sun, but that isn’t exactly the case. Birds can and do survive extremely harsh winters. Like most migratory animals, the primary reason for moving is food. In summer time, food is abundant in northern climates because insects are active and plants and trees are flourishing. When it becomes difficult or impossible to find food, it’s time to go to warmer climates where food is still plentiful.

In northeastern states the American Robin, for example, will arrive in the spring and leave sometime in the early fall. Robins eat worms, beetles, grubs and other such insects, which they aren’t going to find in the cold and snow. You’ll never see a Robin at your birdfeeder; they will not eat foods that sustain some other birds. They need to fly south, or they will starve.

Ducks, geese and other waterfowl are another good example. Their lakes and ponds freeze, making it extremely difficult to survive in their intended environment. To find adequate food, escape predation and maintain their healthy quality of life they’ll move on to warmer climates. They fly in that V pattern to conserve energy, and to improve communication between birds. However, sometimes waterfowl are known to overwinter in cold climates.

So, this tells us why birds fly south, but how do they know when it’s time to go? Does a bird make a conscious decision to fly south? Do birds “follow the food” like some of the migrating animal herds of Africa? Sort of. Scientists say birds likely have an innate response to the reduction in daylight hours, signaling to them that winter is near and they’d better get moving. The exact day they start their journey will be influenced by local weather patterns, but it’s the daylight that gives them the signal to migrate.

Some birds don’t seem to mind the winter. The Black-capped Chickadee, Northern Cardinal, Blue Jay, Tufted Titmouse and others will brave the most brutal cold and snow. Feathers are pretty good insulators, and most birds could make it through a harsh winter if they had to. So if bravery isn’t the reason birds stay through the winter, what is? Again, the reason is their diet. Unlike the Robin, some birds don’t need to rely on the plenty of summer. They can forage for insects in the bark of trees and find enough food to make it through the cold, dark months.

Other birds actually become more plentiful in winter. The Dark-eyed Junco is an example of a bird that will happily inhabit areas other birds have vacated in the winter months. In northeastern states, Juncos will move down from their breeding grounds in Canada to overwinter in a comparatively milder climate.

If a bird is of a species that can find food in the winter, it has no need to migrate. Indeed, there are cases where even Robins will stay through the cold of winter if they can find food. Birdfeeders can help those brave enough to stick out the winter by ensuring they have enough food to survive.

When the birds leave the northern states, where do they go, and how do they know how to get there? Many migrating birds find their way to Mexico or Florida, overwintering in tropical climes. Others simply need climates where the food is abundant enough to sustain them. So how do they know where they are going?

Remarkably, birds seem to possess innate knowledge that helps them to negotiate their long migrations. They are believed to navigate by the sun during the day, and the moon and the stars at night. There is also some research that says they are aware of magnetic fields in the earth, and use them to find their way. It’s a kind of internal GPS, and one of the more impressive abilities in the animal kingdom.

The next question is one I ask of people who move to Florida in the winter: Why do they come back? Again, it’s hardwired into their system. When daylight hours begin to lengthen, birds know it’s time to come back to their breeding grounds. Like many animal behaviors, the whole ordeal is naturally designed to facilitate the survival of the species through procreation.

Birds are everywhere. They’re easy to take for granted, but they really are wonders of nature. The deeper one digs into their behaviors the more interesting they become. This article dealt with North American birds, but there are some amazing bird facts from around the world. Did you know the Bar-tailed Godwit migrates from China to New Zealand in one flight, a distance of over 5,500 miles? Did you know some species of parrots fly 500 miles every day while looking for food? Did you know that researches think there are around 100 billion birds on the planet, and possibly as many as 400 billion? That’s a lot of birds!

Thanks for reading! Now you know a little more about why birds fly south, what they do when they get there, and why some are brave enough to stay through the winter.

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I wrote this artice because I really like watching the birds. I feed them year round, take pictures of them and research them. In fact, the Dark-eyed Junco and Robin's nest pictures on this article are mine (under my copyright, of course). I enjoyed writing this and I hope you enjoyed reading it.