Corncrake fights back from extinction

Few people born in the second half of the 20th century can boast familiarity with the call of a corncrake. A century ago, though, the harsh "crake, crake", simulated by running a finger fast along the teeth of a comb, was a familiar sound of the hay meadows, monotonously rising from the long grass in summer, from dusk into the night. The silence of the species, now driven to virtual extinction in England, is among the most poignant illustrations of the impact of modern farming on our wildlife.

It's no surprise then that the corncrake does not figure in the Farmland Bird Index, a rough government measure used to monitor biodiversity targets. When statistics recently showed populations of representative farmland birds were still falling, a National Farmers' Union official complained that it gave a distorted picture, since it failed to show that magpies and collared doves were doing fine. Magpies and collared doves, should it need to be pointed out, are not dependent on farm-associated habitats. They thrive just about anywhere.

It shows just how far some sectors of the farming industry have to go, despite agri-environmental schemes that have benefited a range of birds like cirl buntings and skylarks, to truly convince in their claims to be guardians of the countryside.

Corncrakes, in the past, have actually been examples of how much man's activities can affect animal populations for good as well as bad. From prehistoric times, the species flourished in old hay-making systems that encouraged its favoured long, dampish, grassland habitats. In the same way, birds of the hedgerow must have thrived during the Enclosure movement, just as those requiring open country took a knock. Bird populations have always waxed and waned. But concerns began to be voiced about corncrakes soon after the mechanisation of farming. By the late Forties, a survey gloomily intoned that "the mowing-machine must stand convicted for the great and continuing decrease… that is still taking place in the British Isles".

The fate of the corncrake, mashed alive by the blades of the mower, is a horrific one. It may be shared by any bird or mammal that nests in fields. But where most of these will eventually scamper off as the machine draws nearer, the skulking corncrake's instinct to remain in cover is taken to such an extreme that it has no escape. "If you're cutting a hay field, the easiest thing to do is to work your way round in a circuit from the outside to the middle," says Charlie Kitchin of the RSPB. "But it means you push the birds into the middle of the field and a lot of them die under the blades of that final cut."

Of course, there is a remedy. You cut your first strip up the middle of the field and work your way outwards, ideally leaving a strip on the edge for the birds to hop into.

But it wasn't mowing methods alone that did it for corncrakes. The switch from hay to silage making, with grass cut earlier and more frequently through the summer, made it impossible to successfully rear young.

The reason for this lies in the corncrake's strange breeding biology, explains Kitchin. "They are birds that hardly fly at all in their day to day movements, yet somehow end up heading off to Africa each winter, facing up to all the predators there, and then flying back again. There's a high mortality rate and very few adults live to return a second year to breed. So virtually the whole breeding population is made up of first-year birds, which means they are vulnerable to a bad breeding season."

It's for this reason that corncrakes have at least two broods a year, laying at least 10 eggs in each clutch. "They are always 'chucking' a large number of young into the system to get very few back," says Kitchin. "Machine cutting and the other changes meant they were lucky to get one brood off, let alone two, so the population collapsed very quickly."

Today, they are effectively extinct from English farmland.They won't return. As Kitchin says, the idea of people going out and cutting the hay with scythes is not going to happen. "Except in parts of Scotland, it's likely that they can only really survive now on large nature reserves."
So the RSPB has been working with the Pensthorpe Conservation Trust, the Zoological Society of London and Natural England on a scheme to bring the birds back to the Nene Washes nature reserve in Cambridgeshire, where Kitchin is site manager.

Hand-reared birds from Whipsnade Zoo have been released into the wild here, and early signs are good. Last summer there were up to 14 male corncrakes calling – probably the largest number to be heard in the south of England for decades.

"This was a place where historically there was always a good population, and there can be again," believes Kitchin. He suggests that if the birds become established, the scheme could be extended to other suitable East Anglian reserves, such as Lakenheath. Corncrakes could be coming home. But don't expect to see them on the Farmland Bird Index.


By Jack Watkins


http://www.telegraph.co.uk/earth/wildlife/5626478/Corncrake-fights-back-from-extinction.html