MISSOULA - Driving along a dirt road, a small falcon may catch your eye.
The American Kestrel is the continent’s most common and widespread falcon. Kestrels typically eat small mammals, such as voles and mice. These prey species are usually well camouflaged and alert so it might seem that the kestrel would have a difficult task catching them, but they have evolved a special hunting ability.
The eyes of kestrels are sensitive to ultraviolet light which is a light spectrum people can’t see. Just because we can't see it doesn’t mean it’s not there; kind of like how a dog can hear the sound of a high-pitched whistle but it’s totally silent to us because it’s outside of a human’s hearing range.
We could walk through a small field hundreds of times and never catch sight of a mouse but the kestrel’s adaptation to see in ultraviolet light (UV) gives them the upper hand. This is because rodent urine actually reflects UV light. Rodents often urinate to mark their territory and foraging routes. So, what may just look like a grassy field to you and me would be lighting up like an airport runway to the predatory kestrel.
You can often see kestrels hovering above a field like a helicopter. They do this to scan large areas of habitat to look for these lit up highways of UV reflecting urine. They look for the areas with the biggest UV glow meaning this is a heavily trafficked area by rodents.
By locating densely populated areas, they increase their chance of success by concentrating their attention where the chances of a kill are highest. When prey is spotted, kestrels hover before quickly diving to the ground to seize it with their talons.
Next time you’re out and about look for these tiny falcons perched on an electrical pole and wires or hovering low over a field.