For Crakes Sake

Ian Bullock. R.B.P.B. Warden: Isle of Coll.

On November 11 th 1991, the Isle of Coll gained some new residents - the Royal Society for the Protection Of Birds (RSPB). The Society purchased about 1000ha (2500 acres) of the Coll Estate at the south-west end of the island which include the Crossapol grazings. Breachacha and Totronald. But why Coll? Why now? And what are their plans?

Why Coll? RSPB was formed over 100 years ago to promote the conservation of wild birds in Britain. Initially they were most concerned about the cruelty involved in killing wild birds for the fashion trade. Later they concentrated on particular species like the Osprey, which became extinct in this country as a result of relentless persecution by gamekeepers and eggcollectors. RSPB is famous for its Loch Garten operation where more than a million visitors have seen the Ospreys breed each year. Round the clock protection and the income from this kind of publicity have helped build the British population of Ospreys up to around 70 breeding pairs. RSPB also spends a great deal of time and money on censusing different species of wild bird. To gauge the health of bird populations, they undertake nationwide surveys to estimate the number of breeding pairs, and then repeat the method ten years later to see if there have been any noticeable changes. Should there be evidence of a serious decline. RSPB follows up the survey with detailed research over several seasons to try and diagnose the cause.

Over the last three decades this has given us a very clear picture of which are the most threatened bird species in Britain. In the last ten years we have compared our data with other international surveys to reveal how these British victims fare elsewhere. From this comes a short list af British birds which, are threatened throughout their global range. There are only three UK species on that list: they are the White-tailed Eagle (the “Sea Eagle" whose wild population is being restored from young birds released on Rhum), the Red Kite (whose stronghold was in Wales but which RSPB has recently released in Scotland also) and the corncrake. The corncrake is an example of a bird which has been pushed to the edge of extinction not by deliberate persecution (though many a crofter has thrown his boot at one in the middle of the night) but by accelerating changes in landscape and technology. There are less than 500 pairs of corncrake in the United Kingdom, half of them in the Outer Hebrides, one third in the Inner Hebrides (where Tiree and Coll form the core area), and a few left in mainland Scotland. The Hebrides are now the last remaining stronghold for the corncrake, and so it is to Coll that the RSPB has come to focus attention on its rescue.

Why Now? One hundred years ago, when fields were commonly cut by scythe and the pace of farming was dictated by the horse, corncrakes were widespread in all the agricultural areas of Britain.The first evidence of a decline started in south-east England in 1850-1875, and became more widespread by the early 1900s. A survey carried out in 1938-39 showed corncrakes still breeding regularly in 19 English and 8 Welsh counties. By 1970 it was down to only 7 English counties, though still common in Scotland. In the last decade the steady decline has continued, down from 750 pairs in 1978 to 600 pairs in 1988, and less than 500 pairs in 1991, with only 4 birds in England , none of which were likely to have bred. Away from the Hebrides the declines in the last ten years have been stark: 72% lost in Orkney and Shetlood, 77% lost from the Scottish mainland. There are still 900 pairs in Ireland, mostly in the north-west counties of Donegal and Mayo, but also in Fermanagh and along the Shannon valley. Elsewhere in Europe the corncrake only survives in any numbers in Yugoslavia (over 1.000 pairs). France (over 2.000 pairs) and Poland (over 4.000 pairs). These are all regions where traditional farming methods have survived longest.

Faced with this evidence of a catastrophic decline in corncrake numbers, in 1985, RSPB, along with other conservation groups, embarked on a three-year research programme in the Outer Hebrides to study corncrake habitat requirements and breeding biology. This revealed something of the private life of this secretive and at times infuriating bird, whose rasping call has kept generations of crofters awake through the short Hebridean night.

The corncrake is well named, “craking” as it does from the cover of grass or cornfield. This unique sound has earned the corncrake its Latin name Crex crex, which mimics its robotic, two-part call. This extraordinary sound is both loud and monotonous, and the bird can keep it up for hours on end, like a telephone that no-one will answer. Unfortunately the corncrake was never blessed with the voice of a nightingale, yet this call is its own peculiar “song”. Only the male crakes: he is defending a patch of ground in which the female will nest, a territory of sufficient size to guarantee food for their brood of young.

Corncrakes are small dumpy birds, less than a foot long, built like quails but more closely related to the moorhen. Despite their short wings and obvious reluctance to fly, corncrakes migrate from here to Africa each year. They leave us in August and September, cross the Sahara, and then move south through East African countrjes like Kenya until they arrive on their wintering grounds in south-eastern Africa in December. Despite this perilous journey, there is no evidence that conditions in Africa have caused their protracted decline in this country. Indeed, felling of woodland in their winter quarters probably means there is more of the grassland that suits them, rather than less. They arrive back in the UK from mid-April onwards. The RSPB study in the Outer Hebrides involved trapping corncrakes and then fitting them with tiny radio transmitters. Birds were then tracked by day and by night to build up a picture of their movements. These radio-tagged birds were still able to mate, lay eggs and raise young sucessfully. Over three seasons a clearer picture of their behaviour emerged.

The one feature that corncrakes need at all times of year is cover. They need vegetation at least 12" tall in which to hide and feed. When they arrive back in April this kind of cover is often in short supply: after a long winter hungry animals have grazed every last tussock to the ground, corncrakes arriving back in late April may have to hide among the irises, sedges and rushes in marshy ground until the grass grows. If this rough pasture has been grazed down too, then they must resort to gardens and cover near buildings where they often fall prey to cats.

If there is sufficient early cover, corncrakes will nest early, from Mid-May onwards. If there is no early cover, they must wait for spring growth so that they can move into long grass to build their nests. The female lays a clutch of 8 to 12 eggs which are incubated for 19 days. The hatched chicks remain with the female for at least 3 weeks until they are independent. If early birds lose their eggs they will lay again, so young birds ere rarely all fledged before the end of July. Throughout this period they move and feed in fields with long grass, which typically are those set aside for hay or silage. This is where the system of grassland management becomes critical. Any trend towards cutting these grass fields early will catch birds on eggs, or will kill young birds still with the female. This is precisely why the move to make silage rather than hay has been so tough on the corncrake. Several of the farmers on Coll have mentioned how the only corncrakes they have actually seen were mangled birds struck by the mower. Birds which are incubating get caught by the blades: the lucky ones are killed outright, the less fortunate may lose both legs and then die a lingering death. Early cutting of hay caused some losses, it is true. but at least the fields were left undisturbed until the harvest. Silage fields tend to suffer more from disturbance, including reseeding and possibly herbicide treatment, harrowing and rolling. Every time a machine goes into the field where corncrakes are nesting it will cause some losses. Another feature of reseeding is that improved grass varieties tend to mature earlier, also leading to an earlier cut with associated corncrake losses. Alongside these changes has come an improvement in farm machinery: modern machines can clear a field in hours where the old cutters would have taken several days with repeated breaks. It all adds up to one thing for the corncrake: nowhere left to hide.

What are our Plans? Some of the lessons from this research study have already resulted in advice for farmers in North and South Uist in 1989, and in Northern Ireland in 1990, where different cutting methods were tested, to try and reduce the number of adults and young killed. It was RSPB's desire to put all these techniques into practice at a single location that spurred them to create this new nature reserve on Coll. RSPB is here because there is still a healthy population of corncrakes on the island, though even here on Coll there is evidence of a decline in recent years. The 1978 survey recorded 28 calling birds: in 1988 this had cropped to 20, in 1990 17 birds were heard, and Andy Knight' s survey in 1991 confirmed that there were between 16 and 21 territories still on Coll. We want to see whether by making small modifications to the existing farming pattern we can reverse this trend and actually increase the number of corncrakes here.

The first thing needed is sufficient cover for the corncrakes when they arrive in April. We will experiment with setting aside small strips or narrow fields, and try and arrange the grazing so that there is sufficient growth in autumn or spring so that they have refuges for shelter and feeding on arrival. We may also experiment with electric fencing round iris beds and along headlands to create extra rough corners for the birds. Ideally such areas should be close to the grass fields where they breed. If we can lure the birds away from farms and homesteads so much the better: for one thing the birds might be less likely to fall victim to cats, and for another, Collachs might get a decent nights sleep!

The second important feature will be to get the hay and silage fields right. We will try out different fertiliser and reseeding mixes until we can create a good stand of mixed grass and herbs that suits the corncrake yet still makes good hay . Too much fertiliser, together with modern grass mixes, tend to produce an early-maturing sward that will need to be cut earlier.

Thirdly we must get the timing and method of cutting right. The easiest way to cut any field is to start at the edge and work in to the centre. This has proved lethal to the corncrake. Birds are driven into the shrinking block of grass in the centre of the field until the final cut finishes them off. This way not only the brood but also the female bird tending them gets slain. We propose either cutting the field in strips (which pushes the "birds across the field) or starting in the middle and working out. which will drive them to the field margins and safety. Leaving a strip around the field edge must help, and if the ever-decreasing circle method must be used. leave about 40 feet square in the middle of the field, which can be taken once the birds have left. The timing of the cut is the hardest thing of all to get right. There is never a perfect time to cut hay. The difficulty of getting hay in at all is one reason why silage has won so many converts. From the birds' point of view, the later the cut the better. We are of the opinion that delaying the cut until August 1st gives the corncrakes the best chance. If this is combined with vigilance from the cutter, and a more flexible approach to the way the field is cut, we should be able to improve the corncrakes chances considerably.

Lastly, we must think of some way to reduce the toll taken by cats. Many islanders keep several cats around their farms to control rats and mice: but there are many tales of them retuming home with corncrakes instead. Perhaps by putting collars and bells on household cats from May onwards, this would give the birds a chance? That way too we can tell which cats seen roaming the fields are truly wild. There is a population of cats living rough in the fields and dunes which may well be a vector in the spread of contagious abortion. Controlling these would give a reprieve to livestock and corncrakes alike.

No doubt the establishment of a nature reserve on Coll will bring extra numbers of visitors to the island. At least the sort of people who care about corncrakes also tend to appreciate the kind of magic an island like Coll has to offer. Even so there will always be a few selfish people prepared to trample through hay fields just to get a look at a corncrake and quite apart from the damage this may cause to crops, it must be stressed that the corncrake is a Schedule 1 species, which means it is protected by law at all times.

We are greatly looking forward to our first year on Coll and hope that the corncrakes respond in a positive way. If any Collacns have any useful advice that may be of help to this special bird. we'd be glad to hear about it.