Falco tinnunculus Linnaeus, 1758

Accepted

Common Kestrel

The Common Kestrel (Falco tinnunculus) is a bird of prey species belonging to the kestrel group of the falcon family Falconidae. It is also known as the European Kestrel, Eurasian Kestrel, or Old World Kestrel. In Britain, where no other brown falcon occurs, it is generally just called "the kestrel".
Common Kestrels measure 32-39 cm (13-15 in) from head to tail, with a wingspan of 65-82 cm (26-32 in). Females are noticeably larger, with the adult male weighing 136-252 g (c,5-9 oz), around 155 g (around 5.5 oz) on average; the adult female weighs 154-314 g (about 5.5-11 oz), around 184 g (around 6.5 oz) on average. They are thus small compared with other birds of prey, but larger than most songbirds. Like the other Falco species, they have long wings as well as a distinctive long tail.
Their plumage is mainly light chestnut brown with blackish spots on the upperside and buff with narrow blackish streaks on the underside; the remiges are also blackish. Unlike most hawks, they display sexual colour dimorphism with the male having less black spots and streaks, as well as a blue-grey cap and tail. The tail is brown with black bars in females, and has a black tip with a narrow white rim in both sexes. All Common Kestrels have a prominent black malar stripe like their closest relatives.
The cere (soft skin surrounding the nostrils), feet, and a narrow ring around the eye are bright yellow; the toenails, bill and iris are dark. Juveniles look like adult females, but the underside streaks are wider; the yellow of their bare parts is paler. Hatchlings are covered in white down feathers, changing to a buff-grey second down coat before they grow their first true plumage.

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 unexperienced 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.

The Common Kestrel starts breeding in spring (or the start of the dry season in the tropics), i.e. April/May in temperate Eurasia and some time between August and December in the tropics and southern Africa.
It is a cavity nester, preferring holes in cliffs, trees or buildings; in built-up areas, Common Kestrels will often nest on buildings, and generally they often reuse the old nests of corvids if are available. The diminutive subspecies dacotiae, the sarnicolo of the eastern Canary Islands is peculiar for nesting occasionally in the dried fronds below the top of palm trees, apparently coexisting rather peacefully with small songbirds which also make their home there.