Why Do Some Birds Migrate?

Watching the geese fly south in their long, pointed formations is a pretty good sign that fall is here. 

Birds migrating south for the winter is a fairly normal phenomenon, especially here in the United States. With so many biomes and so many diverse habitats, there’s a huge variety of migrant birds that travel to and from all corners of the continent. 

Here’s a little bit about migration, migrant birds and, of course, why they end up leaving in the first place!

All you need to know about migrating birds

What is migration?

At its simplest, migration is simply the "seasonal movement from one region to another." Note that the definition doesn’t specifically refer to just birds, though that’s usually what we think of when we are discussing migration. 

Migration is a common occurrence throughout the animal kingdom, from birds who fly south for the winter to wildebeest who follow the rains on the vast Serengeti. The process is part of a very cyclical lifestyle, and it’s deeply tied to the climate, the day-to-day weather and even to human activity!

We’re talking about birds rather than animals here, but many of the factors at play in a bird’s migratory life also appear in other animals’ lives, too — such as food, water, reproduction and weather.  

Types of migration 

Not all migrations are the same, and not all migrant species migrate in the same way. Scientists categorize birds into four main groups based on the distances traveled during migration, though each of these groups still have a wide range of migration types within them.

Permanent residents: These birds do not migrate. Rather, they stay in the same area year-round and are able to find enough food and shelter throughout. Blue jays and northern cardinals are common resident birds in the eastern United States. 

Short-distance migrants: These birds make seasonal travels over relatively short distances, such as moving from the top of a mountain to further down as winter approaches. 

Medium-distance migrants: These birds cover distances of a few hundred miles, whether that be north to south or east to west. 

Long-distance migrants: These birds cross continents each season, sometimes going from as far north as Canada to as far south as South America!

Reasons to migrate

Animals live on a very cyclical pattern that’s heavily based on the natural world around them. They rely on their environments for food, water, shelter, breeding and health, so if their environments are not giving them enough of those necessities, they will eventually move along to a more productive space. 

That’s exactly where migration comes in. 

For a typical migratory bird species, the summer months consist of breeding and rearing their young in a warm, resource-filled environment where there is plenty of food, water and protection from predators. 

As the fall approaches, the days get shorter and the food gets more scarce as the temperatures cool. This signals to the birds that it’s time to follow the warmer weather, which could mean flying south toward the equator, flying down a mountain to lower elevation or even flying into a different biome east or west of their summer homes. 

Birds will then overwinter somewhere there is enough food to keep them alive and healthy—not necessarily in a place that isn’t cold. Hummingbirds, for example, can withstand near-freezing temperatures as long as they can find enough food!

Once the days start getting longer and the temperatures start to rise, birds will migrate back toward their summer homes where they know there will be plenty of food, water, shelter and nesting areas for them to breed, lay eggs and rear their young. 

Then the cycle starts all over again!

It’s also important to note that all these factors (food, water, shelter, predators etc.) can be heavily influenced by the climate and by human activity. Like, for example, destruction of natural habitats, droughts, pesticides, hunting, decrease in insect populations and the like. These, in turn, affect migration patterns which can affect the livelihoods of the species themselves. 

What is a migration hotspot?

If you live anywhere near a peninsula, a clump of islands, a wetland or an oasis of sorts, then chances are that you’re living close to a migrant trap or a migrant hotspot. 

Birds that end up traveling hundreds or thousands of miles during their fall and spring migrations utilize staging areas before completing an especially arduous leg of travel. These staging areas give these birds a chance to rest, eat, gather in large groups or rest from their previous travels. 

These migrant traps are particularly common along the coast, as these areas will either be the last chance to prepare before launching over the water, or the first chance to rest after flying hundreds of miles across the seas. That’s why areas along the coast of the Gulf of Mexico, the Florida Keys, Everglades National Park, Cape May in New Jersey and Point Reyes in California are so popular for birdwatchers, as those are key staging areas for birds who migrate along those paths. 

Common migratory birds

American robin

It’s all about the journey and less about the destination with these birds. American robins are considered to be slow migrants, as they travel up to 3,000 miles over the course of 12 weeks. 

Band-tailed pigeon

Not all pigeons migrate, but these ones are known to spend their winters in California and Texas, then migrate to the Pacific Northwest in the summer. 

Black-chinned hummingbird

These tiny birds are found everywhere from Washington state to Texas in the summer before migrating to Mexico in the winter. 

Canada goose

These migratory birds are migration powerhouses, traveling up to 1,500 miles in a single day! Most Canadian geese travel a total of 2,000-3,000 miles each migration, and can complete their journey south or north in just a few days.

European swallow

You won’t find these birds here in the United States, but they are still fascinating examples of ultra-long distance migrants.

European swallows migrate from one hemisphere to another each season, spending winters in sub-Saharan Africa and summers in Europe. British swallows are known to travel through France and Spain, across the Strait of Gibraltar, through Morocco and across the Sahara desert — before traveling down the continent into South Africa and Namibia. That’s a journey of around 6,000 miles made twice a year!

Penguins

Though you’re not likely to see a penguin running through your town one its way to warmer waters, penguins are a great example of migration in a unique environment. 

Emperor penguins typically migrate inland hundred of miles each spring to raise their young far away from predators along the coast. When summer arrives, the adults and young go back to the sea to eat.

Peregrine falcon

The peregrine falcons that do decide to migrate can travel up to 8,000 miles (one way!) in 9-10 weeks. These birds mate for life and usually go back to the same spot to nest in the spring. Talk about a lot of family road trips!

Ruby throated hummingbird

For such a small bird, hummingbirds can travel an impressive distance in a relatively short amount of time. Ruby-throated hummingbirds live throughout the eastern United States and migrate as far south as Mexico, Panama and Costa Rica — a trip of around 1,200 miles (one-way) done in a span of 1-4 weeks! 

They often use the Texas coast as a staging area before making their long flight across the Gulf of Mexico. 

Snowy owl

Snowy owls usually winter in the northern United States and return to Northern Canada in the spring. These birds are harder to track and, as such, there is little data on migration patterns, but these birds are known to have traveled up to 900 miles in a single migration!

If you live anywhere near a staging area for migrant birds, then you have a unique chance to see some truly amazing groups of birds as they gather and prepare for their long journeys. You can even attract hummingbirds to your garden as they stock up on food for their flight!

Have fun!

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Featured photo courtesy Pixabay/ladymacbeth