Why do birds fly in formation?

Migratory birds can travel thousands of miles across the planet, facing harsh weathers and vast open seas. Migration is a dangerous business.

But every year thousands of pink-footed geese touch down in the UK, and large flocks of finches and thrushes rush overhead. So how do they do it? Well, a lot of them find safety in numbers.

Whooper swans migrate vast distances and find safety in travelling in formation. Photo: iStock

Why do birds fly in formation?

As with flocking together, by flying in formation migratory birds have the advantage of more pairs of eyes to look our for land, shelter or even approaching predators.

And they also have a chance to chat along the way, as birds flying in formation call to each constantly to exchange information.

How do birds form flocks?

Not all flocks are formal family gatherings, some are flocks of convenience. Strangers taking the same migratory routes meet along the way and form a flock – setting off at the same time and drifting along together for a few hours.

Do all birds fly in a V?

No, the famous V isn’t actually the most common formation.

Most flock of birds form a tight-knit oval shape. It is mainly geese, swans and waders that fly in a V formation.

Flying in formation can be a tricky business, and birds don’t always get it right. Each bird in a flock is aware of the birds in front, beside and behind it, rather than trying to monitor the whole flock.

How do birds fly in V formation?

Greylag geese fly in v formation to make migration more energy efficient. Illustration: iStock

In a V, each bird follows on from the wing tip of the bird in front. The leader is not fixed and changes throughout the flight. But we don’t yet know how or when each leader is chosen.

The birds behind position themselves to gain from the upward-moving air (upwash) generated by the bird in front. They constantly manoeuvre to gain the most uplift and time their wingbeats to keep within the upwash.

Flying this way saves birds energy, allowing them to fly further for longer. Monitoring has shown that the heart-rate of birds in V formation is lower than those flying alone, suggesting that flying in a V formation puts less stress on the bird.

You can read more about flock formations on page 19 in your current issue of Nature's Home magazine. Or learn more about how birds' wing shapes and body shapes affect their flight.