Hummingbirds have a unique collision avoidance system built into their brains that allows them to perform high-speed aerobatics in safety, research has shown.

The super-agile birds, whose wings beat up to 70 times a second, can hover, fly backwards, and whizz through dense vegetation at more than 50kph. How they manage to avoid potentially fatal crashes has remained a mystery until now.

Scientists in Canada conducted a series of experiments which showed that the little birds process visual information differently from other animals. As they dart and dive at speed, they judge distance from the way looming objects appear to get bigger, and vice versa.

Other animals, from bees to human motorists, calculate distances from the rate at which objects cross their field of vision.

Hence, a car driver can tell that telephone poles are near because they pass by swiftly. Conversely, far away buildings take more time to move across the visual field, giving an impression of distance.

For this reason, it is difficult to judge the closing speed of an object you are approaching head-on – a lesson taught to all aircraft pilots.

Lead researcher Roslyn Dakin, from the University of British Columbia’s department of zoology, said: “Birds fly faster than insects and it’s more dangerous if they collide with things... we found that hummingbirds use their environment differently than insects to steer a precise course.

“When objects grow in size, it can indicate how much time there is until they collide even without knowing the actual size of the object,” said Dakin. “Perhaps this strategy allows birds to more precisely avoid collisions over the very wide range of flight speeds they use.”

The study, published in the journal Proceedings of the National Academy of Sciences, also showed that hummingbirds use a similar technique as flies to gauge altitude.