[3] It has colonized a few oceanic islands, but vagrant individuals are generally rare; in the whole of Micronesia for example, the species was only recorded twice each on Guam and Saipan in the Marianas.

[4][5][6] The common kestrel was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae under the current binomial name Falco tinnunculus.

[14] Archaic names for the kestrel include windhover and windfucker, due to its habit of beating the wind (hovering in air).

They seem to have radiated in the Gelasian (Late Pliocene,[15] roughly 2.5–2 mya, probably starting in tropical East Africa, as indicated by mtDNA cytochrome b sequence data analysis and considerations of biogeography.

[4] The common kestrels of Europe living during cold periods of the Quaternary glaciation differed slightly in size from the current population; they are sometimes referred to as the paleosubspecies F. t. atavus (see also Bergmann's rule).

The remains of these birds, which presumably were the direct ancestors of the living F. t. tinnunculus (and perhaps other subspecies), are found throughout the then-unglaciated parts of Europe, from the Late Pliocene (ELMA Villanyian/ICS Piacenzian, MN16) about 3 million years ago to the Middle Pleistocene Saalian glaciation which ended about 130,000 years ago, when they finally gave way to birds indistinguishable from those living today.

Other prey species of that time evolved more rapidly (like M. malei, the presumed ancestor of today's tundra vole M. oeconomus), while yet again others seem to have gone entirely extinct without leaving any living descendants—for example Pliomys lenki, which apparently fell victim to the Weichselian glaciation about 100,000 years ago.

Unlike most raptors, they display sexual colour dimorphism with the male having fewer black spots and streaks, as well as a blue-grey cap and tail.

[4] In the cool-temperate parts of its range, the common kestrel migrates south in winter; otherwise it is sedentary, though juveniles may wander around in search for a good place to settle down as they become mature.

The common kestrel readily adapts to human settlement, as long as sufficient swathes of vegetation are available, and may even be found in wetlands, moorlands and arid savanna.

The global population has been fluctuating considerably over the years but remains generally stable; it is roughly estimated at 1–2 million pairs or so, about 20% of which are found in Europe.

[4] When hunting, the common kestrel characteristically hovers about 10–20 m (35–65 ft) above the ground, searching for prey, either by flying into the wind or by soaring using ridge lift.

Other suitably sized vertebrates like bats, swifts,[26] frogs[citation needed] and lizards are eaten only on rare occasions.

Generally, invertebrates like camel spiders and even earthworms, but mainly sizeable insects such as beetles, orthopterans and winged termites will be eaten.

[4] The common kestrel requires the equivalent of 4–8 voles a day, depending on energy expenditure (time of the year, amount of hovering, etc.).

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 with small songbirds which also make their home there.

The eggs are abundantly patterned with brown spots, from a wash that tinges the entire surface buffish white to large almost-black blotches.

In "Into Battle" (1915), the war poet Julian Grenfell invokes the superhuman characteristics of the kestrel among several birds, when hoping for prowess in battle: The kestrel hovering by day, And the little owl that call at night, Bid him be swift and keen as they, As keen of ear, as swift of sight.

Gerard Manley Hopkins (1844–1889) writes on the kestrel in his poem "The Windhover", exalting in their mastery of flight and their majesty in the sky.