We’ve all seen the majestic sight of an eagle or hawk gliding high in the sky before diving down for their dinner. But have you ever seen a raptor stay motionless in the air?
If so, you’ve probably seen a kestrel! Kestrels are a unique group of falcons linked not by a common ancestor, but by their ability to “windhover,” or remain seemingly motionless in the air while looking for food. This ability helps them hunt in open places where a perch might not be available for them to get a good vantage point. How they do it, though, is through the physics of balance and lift.
Kestrels fly up high and then turn into the wind, perfectly matching the speed of the oncoming air. As they fly upwards, they fan their tails out and tilt them down, allowing them to pause in midair. Meanwhile, they use the slotted feathers on their wings to reduce turbulence, keeping themselves steady amid the ever-changing wind. Throughout the process, these movements are so precise that the kestrel’s head remains perfectly stationary.
As they continue to hover, they adjust the tips of their wings ever so slightly to account for the wind, generating lift while minimizing their flapping. The more wind there is, the fewer motions the bird needs to make because the increased lift from the higher windspeed holds them in place. When the bird doesn’t need to flap at all, scientists refer to it as “kiting” because of its resemblance to toy kites.
So, the next time you’re birdwatching, keep an eye out for a humble kestrel!