Have you ever seen a bird hover in midair, defying gravity? It’s a mesmerizing sight, especially when it’s a bird of prey like the kestrel. While hummingbirds and insects are well-known for their hovering abilities, larger birds of prey usually rely on gliding to maintain altitude. But the kestrel is a unique exception – it can actually hover! Let’s explore the incredible art of “windhovering” and understand how kestrels master this impressive technique to enhance their hunting efficiency.
The Science Behind Windhovering
Unlike smaller hummingbirds, kestrels can’t beat their wings fast enough to generate the lift required to keep them aloft. Instead, they face into the wind and let it do the work for them. This precise technique allows their heads to remain completely still, making them ten times more efficient hunters.
In average wind speeds, kestrels can glide comfortably while flapping their wings at a leisurely pace. However, their forward movement is canceled out by the wind, keeping them in the same position. Even the tail of the kestrel plays a crucial role. The already broad tail is spread out and slightly depressed, increasing the surface area exposed to the oncoming wind. This tail depression becomes more evident as the kestrel prepares to hover.
Before hovering, kestrels glide for a brief moment and then shoot upwards. During this upward movement, their wings remain outstretched, but the tail is tilted downwards. The depression of the tail feathers helps halt the kestrel in midair, checking its forward momentum.
The Wings and Feathers that Make it Possible
The design of the kestrel’s wing feathers is equally vital for their ability to hover. Like other birds of prey, kestrels have slotted high-lift wings, which help reduce turbulence during hovering. These slots allow air to pass through, enabling the kestrel to hover instead of stalling.
In high winds, kestrels have an easier time, as flapping is reduced to a minimum. In even stronger winds, they may not need to flap at all, simply opening their wings and gliding into the wind – a technique known as “kiting.”
Hovering Without Wind – A Balancing Act
While the term “windhovering” implies the use of wind to hover, some sources suggest that kestrels can hover without any wind at all. Their bodies are shaped in a way that, with outstretched wings, they automatically glide forward. The forward movement is then countered by rapid wing beats, with the downstroke slightly oriented forwards. This “banking” motion pushes the kestrel back, neutralizing the forward movement. However, hovering without wind requires a delicate balancing act. When a kestrel loses its balance, it tends to slip forward before regaining control and hovering again. On average, kestrels slip about three times before either moving on or circling back to attempt another hover, depending on the possibility of finding prey.
In conclusion, watching a kestrel windhover is nothing short of impressive. Their mastery of this unique technique sets them apart from other birds of prey and showcases their remarkable adaptability. So, next time you spot a kestrel in action, take a moment to appreciate the grace and skill required to hover effortlessly in the air.
Sources: Read Book Online and Paul D. Frost
