When hunting, the Common Kestrel characteristically hovers about 10 - 20 m (c.30 -70 ft) above the ground, searching for prey, either by flying into the wind or by soaring using ridge lift. Like most birds of prey, Common Kestrels have keen eyesight enabling them to spot small prey from a distance. Once prey is sighted, the bird makes a short, steep dive toward the target. It can often be found hunting along the sides of roads and motorways. This species is able to see near ultraviolet light, allowing the birds to detect the urine trails around rodent burrows as they shine in an ultraviolet colour in the sunlight.Another favourite (but less conspicuous) hunting technique is to perch a bit above the ground cover, surveying the area. When the birds spot prey animals moving by, they will pounce on them. They also prowl a patch of hunting ground in a ground-hugging flight, ambushing prey as they happen across it. Common Kestrels eat almost exclusively mouse-sized mammals: typically voles, but also shrews and true mice supply up to three-quarters or more of the biomass most individuals ingest. On oceanic islands (where mammals are often scarce), small birds - mainly passerine - may make up the bulk of its diet while elsewhere birds are only important food during a few weeks each summer when inexperienced fledglings abound. Other suitably sized vertebrates like bats, frogs[citation needed] and lizards are eaten only on rare occasions. Seasonally, arthropods may be a main prey item. Generally, invertebrates like camel spiders and even earthworms, but mainly sizeable insects such as beetles, orthopterans and winged termites are eaten with delight whenever the birds happen across them. F. tinnunculus requires the equivalent of 4 - 8 voles a day, depending on energy expenditure (time of the year, amount of hovering, etc.). They have been known to catch several voles in succession and cache some for later consumption.
