Common Kestrel (Falco tinnunculus)
To many people in Europe, the Kestrel is their only truly familiar bird of prey. It is the one that is easy to spot as it hovers over motorway verges or above waste ground in city centres. It is one of the few raptor species found in gardens or local parks, and in farmland. It doesn’t need mountains, or large forests, or rocky hillsides in which to thrive, like so many others. It is neither shy, nor retiring, and it isn’t difficult to identify. Its abundance brings it to people’s attention.
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A fair selection of other European raptors will hover, either commonly or occasionally, but none are as closely associated with this form of flying on the spot as the Kestrel. The impression is correct; most Kestrels practise this as their most frequent type of hunting. They fly at a moderate height over the ground, wings flapping rapidly and tail fanned, with the head held extraordinarily still as they scour the ground for movement. If something appears they will often break from a hover, drop down slightly and resume hovering again; the final strike is a quick plunge to the ground and a grab with the talons. At times they will perform a similar strike, but begin their plunge from a perch.
Although Kestrels have a catholic diet, most individuals feed by choice on rodents, especially voles. These small mammals live in long grass and are active by day. It has recently been discovered that a vole’s urine leaves an ultraviolet trail than can be detected by Kestrels, thus giving the hunters a distinct advantage in catching them. In the northern parts of the Kestrel’s range the numbers of voles vary from year to year on a four-year cycle, and the breeding success of the falcons follows suit.
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Although Kestrels are very much in the diurnal raptor group, they are far more successful than most others in the family at hunting by twilight or by moonlight. Males often do this is the spring when they are trying to feed both their mate and the nestlings, and their workload is heavy. At such times their prey that they seek changes; nocturnal mammals such as Wood Mice are taken, and young Rabbits occasionally, too.
It would be wrong give the impression that Kestrels only hunt small furry mammals. Insects are often important, especially in the warmer parts of the Kestrel’s range, and lizards make a good meal, too. Some individuals also seem to be adept at catching birds, although they are in the minority. When hunting, these experts use the same ambush technique as the Sparrowhawk, using a surprise strike from a concealed perch. But most Kestrels are not very good at this.
The Kestrel will feed over almost any kind of open country, but it needs suitable nest sites nearby if it is to take up residence and breed. Three distinct types of site exist: some birds nest in holes in trees, others on cliffs and still others in the old nests of other birds such as Crows. In recent times a fourth has been added: artificial sites. Kestrels have no problem at all in using large nest-boxes, and the provision of boxes may lead to local increases in population.
By Alexis Lours – Own work, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=114354664
It is possible to tell that a pair of Kestrels is intending to breed well before it actually does so; the birds start displaying in the air in February, even though they may not begin to attend the nest for another two months or more. Display-flights are accompanied by much hoarse trilling. High in the sky the male makes repeated mock attacks upon the female: he dives towards her and she dodges him by a rapid roll to the side. Later on the male may perform alone, flying along with erratic wing-beats and rolling from side to side to show off its whitish underwings. Kestrels form monogamous pair bonds, and the male spends a great deal of its time provisioning its incubating and brooding mate with gifts of food.
Most Kestrels live in small home ranges and nest well apart, although in some areas colonies will form, like those of Lesser Kestrels. If the immediate countryside can support them, a pair will sometimes remain around the breeding site all year, but many move away instead to take up a feeding home range on their own. The Kestrel is a migrant in the northern and eastern parts of its wide range in Europe. Clever though it is in finding prey in the long grass, snow is an impenetrable barrier to a hunting Kestrel, forcing it to move elsewhere.
From ‘Birds: A Complete Guide to All British and European Species’, by Dominic Couzens. Published by Collins and reproduced with permission.