Birds are, without a doubt, some of nature’s most fascinating creations! They have so many adaptations and specializations that we could write thousands of articles and cover not even 10% of how awesome they are!
Today, we’ll discuss migration – why do birds travel thousands of miles, and where do they fly?
Bird migration is prompted by cooling weather conditions, food availability, enhanced breeding opportunities, and genetic predispositions.
Obviously, that’s a short answer to a complex question. So if you want to discover more, don’t hesitate to keep reading!
Table of Contents
Why Do Birds Migrate?
Bird migration is the seasonal movement birds engage in to fly toward specific destinations during particular periods of the year.
It’s worth mentioning that not all bird movements are considered migrations. Scientists argue that only the travels marked by their annual seasonality should be regarded as migratory patterns. In short, if birds engage in irregular trips around their habitats or perform a one-way trip, these movements aren’t considered true migrations.
When we first think of bird migration, we automatically associate it with cold weather. When temperatures drop, birds fly toward warmer places to survive. Well, this is true, but that’s not the whole truth.
The main reason why birds migrate is that once the temperatures drop, food becomes scarce. The thing is that many migratory birds may choose not to fly south for the winter if food is enough! That’s because migration is an enormous risk birds take. On their routes, they’re much more susceptible to predation, hunger, and exhaustion.
Another reason some birds migrate is associated with the length of summer days. The farther north you go, the longer summer days are.
This is an advantage for diurnal breeding birds, as the clutches they produce are typically larger than the clutches of resident birds. Besides this, it has been reported that insects are more abundant in the north during the summer. This migration is common in birds that overwinter in the tropics.
Migration may also be triggered by genes and instincts. The first bird migrations were recorded approximately 3,000 years ago, so it’s no wonder this survival urge to leave is so deeply rooted in a bird’s instinctual system!
Many people who keep birds as pets report that around the time their species is supposed to start their migratory route, the birds were restless and kept trying to fly out of the cage. There’s even a scientific term used to call this migratory restlessness – zugunruhe.
Why Do Birds Migrate in Large Flocks?
Most birds migrate in large flocks because this ensures better protection against predators. A large bird flock is less likely to be attacked by a predator than a single bird. Besides, even if they’re attacked, they can work their way out of this confrontation by sticking together, possibly confusing the predator.
Another reason why flock migration is an excellent idea is linked to the energy birds use to fly. It has been proven that birds flying in groups use less energy than those flying alone. V-shaped formations are the most efficient, as the birds conserve up to 20% energy.
When arranged in a V-formation, the birds take advantage of the upwash lift force produced by the lead bird. The upwash helps the bird maintain its own weight. This way, each bird helps the bird behind it fly more easily.
To take advantage of this, they must position themselves behind and slightly to the side of the bird in front of it. Then, they have to flap their wings just in time to catch the upwash. This behavior has been proven for ibises and is likely similar in other long-winged birds like geese and pelicans.
This alignment is likely done by sight or by sensing the air currents. However, scientists aren’t sure this is the only way. We’ve all convinced ourselves that birds are much more complex than anyone suspects, so they may have a secret way of making this V-shape work perfectly!
Why Do Birds Migrate at Night?
Some birds engage in nocturnal migratory behavior because this minimizes predation and prevents them from overheating. Additionally, they can take a break during the day and spend some time foraging.
On the other hand, there’s a huge disadvantage as well – the loss of sleep. A study on the migratory sleeplessness of white-crowned sparrows showed that the birds that engaged in nocturnal migratory patterns spent ⅔ less time sleeping.
However, these fantastic creatures adapted even to the loss of sleep! Scientists observed that although they didn’t sleep enough, this didn’t alter their cognitive functions.
Types of Bird Migrations
Birds engage in two types of migrations:
- Long-distance migrations
- Short-distance migrations
Long-distance migrants are the birds that fly seasonally between their wintering and breeding grounds. Some species, like the Arctic tern, are known to fly more than 20,000 km (12,400 miles) following a migratory route!
As the term implies, short-distance migrations are much shorter. This behavior is often observed in birds living in the tropics. Tropical hummingbirds, for example, move altitudinally if food becomes scarce. Mountainous species often migrate altitudinally to avoid the cold. Some species travel distances as short as 5 km (3 miles) away from their natural habitats.
Short-distance migrants are also known to adapt better to changing climatic conditions, while long-distance migrants are more susceptible to weather changes.
Do Hummingbirds Migrate?
Of 366 hummingbird species, only 15 are migratory. Many North American hummingbird species, like the rufous hummingbird, travel south to Mexico for the winter. Others, like Anna’s hummingbird, are year-round residents and rely on their adaptations to survive harsh temperatures.
Do Crows Migrate?
Crows are only partially migratory, meaning that some populations are year-round residents, while others prefer to migrate.
Do Robins Migrate?
The answer to this question depends on what species and population we’re discussing. Take the European robin, for instance. Some populations, primarily those in Western Europe, are year-round residents, while others fly south to Europe or North Africa to overwinter.
Do Blue Jays Migrate?
Some blue jay populations migrate, but scientists aren’t entirely sure what prompts their migratory behavior and how they establish their routes. They’ve been observed flying along the Great Lakes and Atlantic coasts while migrating.
Besides this, they do not engage in annual migrations – this year they’ll migrate, and next year they’ll stay put.
Other blue jay populations are year-round residents.
Do Woodpeckers Migrate?
Most woodpeckers are year-round residents. Only a few species, like the yellow-bellied sapsucker and the rufous-bellied woodpecker, engage in migratory behavior. The gray-capped pygmy woodpecker is an altitudinal migrant.