Kestrel: On a wing and a prayer

Once Britain’s most common bird of prey, the kestrel has suffered an alarming decline in recent years. Charlie Elder finds out if the motorway falcon is on the verge of a crisis.

 

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Kestrels article spread

Once Britain’s most common bird of prey, the kestrel has suffered an alarming decline in recent years. Charlie Elder finds out if the motorway falcon is on the verge of a crisis.

 
From a distance the lone bird hovering over the moor looked like it had been pinned to the sky. Rapidly beating its wings as if trying to break free, it remained fastened just above the horizon.
 
Then it dropped slightly, stalled and turned, catching the light headwind and sweeping in an arc before rising to a new position, tail spread and eyes locked on the ground below.
 
Unmistakeable. A kestrel. There is nothing else quite like it. Our most widespread falcon may not be able to compete with other birds of prey in terms of size, speed or sheer majesty, but it has probably inspired more people to take up birdwatching than the osprey, peregrine and golden eagle combined.
 
Roadside friend
 
For many in the UK, the ‘windhover’ is the first raptor we identify or have pointed out to us: a cruciform silhouette suspended over heaths and headlands, moors and motorway verges, its fanned wings weaving sense out of the breeze.
 
Instantly recognisable, common and conspicuous, it has earned a place in our hearts as a familiar friend.
 
Yet when I spotted a kestrel over Dartmoor recently, it took me by surprise. As I watched the handsome male hunting, his back the colour of toasted cinnamon in the sun, I realised that I hadn’t seen one in the area for some time.
 
That the encounter felt like a rare privilege said something about the species’ steep decline in Britain in recent years. It seems that we can no longer take our kestrels for granted.
 
A resourceful falcon
 
The fortunes of this unassuming ‘mouser’, once considered by falconers to be worthy only of a knave, have fluctuated over the past century along with those of most other British birds of prey.
 
Persecution by gamekeepers took its toll, despite the kestrel’s usefulness as a rodent killer, until a period of respite during the two world wars, followed by legal protection, enabled the species to gain ground.
 
But the introduction of organochlorine pesticides such as DDT into the food chain in the mid- 20th century dented its numbers again, notably in the east. The intensification of farming over the decades that followed posed another threat as vole-rich grassland and field margins went under the plough.
 
Secret to success
 
It is testimony to the kestrel’s resourceful nature that it has stayed a ubiquitous part of our national fauna despite these setbacks. It nests everywhere from remote cliffs to city window ledges, its shrill ‘kee-kee-kee’ cries bringing a touch of the wild to industrial wasteland, and the sight of this hunter perched beside a main road or railway embankment always lifts a dreary scene.
 
Central London has been home to the species since the 1930s; a pair even nests in the garden of 10 Downing Street (see below). One of the adults could be heard calling in the background during David Cameron and Nick Clegg’s historic outdoor news conference after this May’s General Election, prompting Clegg to look up to see the cause of the noise.
 
Voles on the menu
 
Kestrels hunt other birds, especially in urban areas, as well as beetles, worms and a variety of small mammals. But their favourite prey is the short-tailed or field vole, which thrives in scruffy sward such as road verges.
 
Adult kestrels cannot afford to invest too much time and effort in a random search for voles. Instead, their excellent eyesight, which is sensitive to ultraviolet light, enables them to detect urine trails around the burrows of their prey (the trails reflect UV light). They can thus target areas with the highest densities of voles.
 
Studies show that kestrels reduce the demands of energy-sapping hovering by incorporating tiny pauses, stretching their necks forwards to compensate as they are blown backwards, yet managing to prevent their heads from moving more than a few millimetres out of position. Brakes on, engine revving, the hovering technique looks exhausting but is undoubtedly effective.
 
Trading places
 
When I started watching birds in the 1980s, kestrels were an everyday sight (back then, the estimated UK population was 52,000 pairs), and so I soon gave up pointing them out to passengers on long drives, saving my enthusiasm for buzzard sightings instead.
 
Today, the opposite is the case: buzzards comfortably outnumber kestrels.
 
According to the most recent Breeding Bird Survey figures, the UK lost one-fifth of its kestrels between 1995 and 2008, and a further 36 per cent in 2008–09. Overtaken by both the buzzard and sparrowhawk, the motorway falcon is no longer our most common bird of prey, and I have begun to raise a finger from the steering wheel in its direction once more.
 
Downward turn
 
Last year’s sudden steep decline in kestrel numbers is worrying, but the long-term downward trend is more significant, since it irons out any short-lived effects of harsh winter weather or boom-and-bust cycles in vole populations.
 
Kestrels are able to raise up to five chicks per year when food is plentiful, so their populations can rapidly recover – but this doesn’t appear to have happened in recent years.
 
The BTO’s Atlas of Breeding Birds painted the country almost entirely red with kestrel territories 20 years ago. Scattered sightings plotted on a provisional new distribution map now look more like a mild case of the measles.
 
It’s lonely at the top
 
Life at the top of the food chain is often a precarious one, and the plight of any predator tells a story about the health of its environment. The good news is that almost all of our day-flying raptors are on the up and up, due largely to conservation efforts and reduced persecution and pesticide use.
 
Buzzard numbers, at one time depressed by the spread of myxomatosis in rabbits, are now soaring; reintroduction schemes have helped red kites to regain lost ground; and hobbies are thought to be taking advantage of an increase in their dragonfly prey to spread northwards.
 
The peregrine population has more than trebled since the 1960s, when it was decimated by the eggshell-thinning effects of DDT. Sparrowhawks have fallen back slightly since 2005 according to counts by BTO volunteers, though not on the scale of the kestrel’s losses, which are not only severe but present something of a puzzle.
 
So what's the problem?
 
Formerly, the problem could be blamed on agricultural intensification, particularly the conversion of rough grazing to improved pasture (which supports fewer rodents). But farming has not become more intensive over the past few years, and many landowners have adopted agri-environment schemes to help wildlife, for example by leaving field margins uncultivated and unsprayed.
 
Kate Risely of the BTO says that new data highlighting changes in kestrel numbers is just a starting point, and further research into possible causes and solutions is needed. “The decline may simply reflect a few bad years and the population could yet recover, or it might be an early warning of a major downward trend,” she explains.

 

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