Some birds fly a wedge, and others don't. What's the difference?

The most famous wedge-flying birds are cranes, swans, geese and ducks. But they're not the only ones. This order is typical for many migratory birds - lake gulls (in some regions), pelicans, cormorants and others.

Why do birds fly a wedge?

It has long been known that a wedge can significantly save energy for birds - from 20% to 30%. In what way?

It's all about the airflow. The leader of the pack flies in front and, making a wing swing down, forms a jet of air for the birds flying behind. This air stream catches up with them, helping them fly forward. That is why the strongest individuals are at the head of the wedge - they bear the most of the aerodynamic load; at the end of the wedge there are younger and weaker birds.

Why aren't all migratory birds flying a wedge?

If a wedge helps to fly by reducing the load on birds and helping more individuals overcome it, then why aren't all birds flying the same way?

At the beginning of the article, some of the birds lined up with a wedge were mentioned. All of them are quite large - for example, the river gull weighs 200-350 grams, and the crane so in general over 5 kg. Therefore, it is assumed that it is the high weight that affects the choice of wedge as a method of flight. Less weight, the wingspan of birds does not allow to create a strong enough air flow for individuals flying for the leader.

It is also possible that small birds have more advantages by flying in a flock rather than a wedge. For example, it provides greater safety by preventing birds of prey from attacking.

But there are also those among the big birds who avoid the wedge. Okay, storks also make it easier for them to fly with air. But they don't adjust to the air currents from the flying congeners ahead, but use thermal currents.