Kestrels (falco tinnunculus) are one of the best known, and best loved, birds of prey in the UK and are instantly recognisable by their unique ability to hover in situ above prey, their pointed wings and fanned tail feathers. Kestrels are the most common bird of prey in Europe, although it appears that the numbers are in slight decline in the UK. Kestrels are also considerably smaller than other common birds of prey such as the red kite or sparrow hawk.
According to the IUCN, kestrel numbers are declining, but they are classified as a species of least concern. However, this classification applies to worldwide kestrel populations. In the UK, the kestrel is included on the RSPB Amber List of Birds of Conservation Concern.
It is an offence under the Wildlife and Countryside Act 1981 to kill or injure kestrels or to damage an active nest.
The RSPB estimates that there are around 46,000 mating pairs in the UK.
There have not been any extreme fluctuations in kestrel populations. However, there was a slight decline in the 1970s, thought to be attributable to changes in farming practices. The kestrel rapidly adapted to industrialisation and urbanisation; they have now learned that tractors often flush prey and watch farming operations. They are also able to survive in cities.
Kestrels are pervasive and have adapted to most environments save areas dense with trees or large areas without any trees. Kestrels often use trees to perch whilst locating their prey at considerable distances. A kestrel can see and catch a beetle from 50 metres.
The kestrel is also known as the Wind Hover. Gerard Manley Hopkins wrote a poem called ‘The Windhover’ and describes his delight at watching the hovering bird.
Generally, kestrels are solitary but can sometimes be seen travelling in flocks of up to ten individuals at sources of abundant food or during migrations.
Kestrels typically eat small mammals and birds, typically voles. Kestrels need to eat around six voles per day and therefore it is not unusual for kestrels to catch several voles in one hunt and to cache some for later. This allows kestrels to save energy as hovering while searching for prey is energy intensive.
In cities, kestrels eat more birds than mammals, which are scarce in urban areas.
The kestrel has sharp vision and can detect UV light which it uses to follow traces of urine left by voles and locate their prey.
In February the breeding season begins with display, courtship and finally the formation of a mating pair. The female will then lay 3-6 eggs in April or May (with a couple of days between each lay), although in years of reduced food availability females may not lay at all.
The incubation period is just under a month per egg and therefore the eggs hatch at differing times and require constant brooding for the first 15 days, until hatchlings can control their own body temperature.
Unusually, there is no aggression between chicks which often stay together for some time after fledging. However, mortality in young birds is quite high. Only 20 per cent of young kestrels will reach the age of two, when they will secure their own mate and territory.
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