The barn owl is one of the most cosmopolitan of all birds, living in open grasslands, marshes and agricultural land over most of Europe and Africa, in parts of the Middle East, in much of the Indian sub-continent, through Southeast Asia to Australasia and in the Americas. It owes its remarkably wide distribution partly to its ability to live in habitats modified for farming. Indeed, it is probably fair to say that the barn owl has gained from humanity’s clearing of forests, enclosing land, storing large amounts of grain which attracts rodents and by providing nest sites, for example, in buildings. In Britain, the birds have long enjoyed a special status as the ‘farmer’s friend’ and have been regarded with particular affection.
Barn owls are not critically endangered, but they are on the decline in Britain, elsewhere in Europe and in parts of the US. Most conservationists agree that in Britain the decline has been caused mostly by the drastic reduction in foraging habitat brought about by ever more intensified agriculture. The loss of suitable habitat continues, particularly through urbanisation, road construction and land drainage, and the loss of farm buildings as nest sites. Pesticides such as difenacoum and brodifacoum brought in to control rodents resistant to warfarin may also be damaging the birds. Figures published by the Institute of Terrestrial Ecology in Britain show that barn owls are sensitive to, and frequently exposed to, these chemicals.
So to conserve barn owls we need to restore prey-rich hunting ranges of rough grassland, secure nesting sites and control the use of rodenticides. Yet most media attention has focused on schemes involving the captive breeding and release (CBR) of barn owls. These schemes aim to top up or reinstate wild populations from captive stocks.
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Sadly, in Britain the vast majority of schemes fail to fulfil all, or in most cases any, of the guidelines laid down by the UK Committee of the International Union for the Conservation of Nature for reintroductions and restocking. Most strikingly, the majority of schemes ignore the fact that captive-bred birds can found or replenish wild populations only if conditions in the wild are suitable for the species and if the methods of release enable captive-bred birds to survive in the wild. Because there is no legal necessity to monitor the schemes, it has been difficult to determine just how successful these projects are.
In Britain, the number of CBR schemes is staggering. The Hawk and Owl Trust estimate that in England and Wales at least 3000 barn owls are released each year by more than 600 amateur operators, into a wild population estimated at only about 4500 pairs.
David Ramsden of the Barn Owl Trust recently estimated that there are 20 000 to 30 000 barn owls in captivity in Britain. Some of these captives are wild birds injured in collisions with vehicles, resulting in a growing captive population of permanently disabled birds that cannot be rehabilitated but can still breed. Some young birds are sold at between £40 and £80 a pair through avicultural magazines and in pet shops throughout Britain, but the rest are either released or used as breeding stock. Sales of closed metal leg rings provide one of the very few reliable indices of trends in the numbers of barn owls sold or released into the wild, although it is likely most are released without rings. The suppliers of the rings, the British Bird Council, report a steady increase in sales from 1000 in 1983 to more than 6000 in 1990.
Barn owls can be bred in captivity and sold for profit because, while the species is listed on Schedule 1 of the Wildlife and Countryside Act, 1981, (meaning that wild barn owls have the maximum protection available in law) it is also included in Schedule 3 as a bird ‘which may be sold alive at all times if ringed and bred in captivity’. No other species of owl in Britain can be sold without a licence. At present there is no legal requirement for either captive-bred barn owls or their breeders to be registered in any way, nor for released birds to be ringed.
Nor is there any control over the circumstances in which birds are released. Guidelines for would-be releasers are available from the Barn Owl Trust and the British Owl Breeding and Release Scheme (BOBARS), but methods of releasing captive bred barn owls vary enormously. The vast majority of release schemes probably involve only one or two non-sponsored, enthusiastic aviculturalists with an interest in barn owl conservation. The Barn Owl Trust is one of the very few organisations to attempt to evaluate the success of different release methods and to publish their results. They presently operate two release methods.
In ‘long-term release’, a pair of captive-bred owls are confined in a suitably adapted building for a period of months and allowed to breed. When the owlets are four weeks old the adults are released and supplementary feeding is continued for a period of months. In ‘young clutch release’, a brood of owlets approximately five weeks old are placed in a nestbox within the building. These are fed for a period of months. No adults are present, the young are not confined and the owlets fledge when they are about eight weeks old. This method encourages a pattern of returning for food so that the owls disperse gradually or stay at the release site. But the number of owls released from the larger, well organised schemes make up only a fraction of the total, and other CBR schemes are less thorough. The great majority of barn owls are reared in captivity and then simply released into the wild to fend for themselves. The Barn Owl Trust says that it does not expect captive barn owls that are simply ‘let go’ to survive and has published data to prove this.
The British Trust for Ornithology has compared the survival and dispersal of first-year and adult captive-reared barn owls with a sample of wild birds ringed between 1982 and 1987. The results show that captive-reared barn owls are much more likely to die as adults or in their first year than wild birds. On average, only 10 per cent of the captive-bred birds in their first year and 15 per cent of adults survived, compared with 19 per cent and 55 per cent respectively in the wild population. On this evidence, only a very small proportion of the captive-released barn owls live long enough to breed in the wild: most die soon after release. The British Trust for Ornithology study concluded that it was very unlikely the release of captive-bred barn owls was boosting the wild population at all. So even if thousands of barn owls are being released each year, very few live long enough to breed, so their effect on the population is negligible.
The study also showed that captive-bred birds die for different reasons. More of the first year captive-released birds are killed by traffic and more of the captive-released adults die from starvation than wild populations. Moreover, The British Trust for Ornithology study suggests that a lot of barn owls are released into a totally unsuitable habitat, that they leave these areas rapidly and that most of them die within a few months mainly from starvation.
Some individual CBR schemes claim limited success, and certainly some release methods are more successful than others in prolonging survival. Figures published by the Barn Owl Trust show that the young clutch method is unlikely to result in the establishment of barn owls at the release site. However, they also show that pairs of captive-bred barn owls which are confined to a building and allowed to breed before being released show some fidelity to their release site. Some breed the following year, particularly if supplementary food is provided. But the survival of captive-released birds is not proof that they have been successfully recruited into the wild breeding population. In the US, conservationists have suspended CBR programmes in Missouri, Iowa and Wisconsin, pending a review and evaluation of the results of previous, limited restocking attempts. Carl Marti, an expert on barn owls in the US, concludes that attempts to restock the birds where they have declined do not seem to have been effective.
CBR schemes may be harmful in several ways. Clearly, if most of the barn owls released in Britain die in their first year, as the British Trust for Ornithology data suggests, one can ask whether it is ethical to continue these programmes, on grounds of animal welfare. But even if many of the released birds did survive, they might harm the existing population. Releases could damage the established population by introducing new, possibly alien or inferior genetic material into the wild barn owl population. For instance, barn owls of South African origin are being offered for sale in Britain and may be involved in releases. Whatever the origin of released birds, they might compete with wild barn owls for scarce resources, particularly if CBR schemes are conducted in areas where the wild population is already at capacity.
Another worry is that the birds are not being screened by vets for disease before release. There are many well-documented examples of the disastrous effects of introduced birds bringing disease to wild populations. In Hawaii, for instance, exotics carried avian malaria, which was transmitted to vulnerable endemic species, causing some to go extinct.
One of the most serious deficiencies of barn owl CBR schemes in Britain is the lack of any form of registration. At present there is no way of knowing what proportion of the free-living population are wild birds or the proportion of captive-bred birds. The greatest safeguard against environmental disasters, such as the pesticide-related decline of peregrine falcons in 1957 to 1963, is regular, reliable monitoring of a population. But the uncoordinated release of thousands of barn owls every year in Britain makes it extremely difficult to place any meaningful interpretation on census statistics and also makes it impossible to monitor the impact of rodenticides, habitat changes, conservation initiatives or any other environmental variable that might affect population levels.
So substantial investment of resources and effort in release schemes for barn owls in Britain is of little or no conservation value. That is not to say that CBR schemes can never make a contribution to the conservation of barn owls: it is simply that, on the evidence available, captive release is not the management option that offers the best chance of increasing wild barn owl populations. Conservationists should focus their efforts on identifying and tackling those factors presently limiting the wild population. Conservation initiatives should focus on the restoration of foraging habitat, backed up by nestbox schemes, education and advice on the safe use of rodenticides. Recent reforms to the Common Agricultural Policy to reduce agricultural yields could offer the economic incentive for habitat creation. Extensions of managed set-aside, together with recently ammended additions to the network of environmentally sensitive areas, offer opportunities for the restoration and recreation of rough grassland habitats, which should prove valuable to barn owls.
Reintroduction programmes are likely to be worthless unless steps are taken to improve habitat; once habitat is improved, restocking may well be unnecessary anyway, given that the barn owl is still relatively widespread. Restocking and reintroduction should be regarded as a last resort when all other conservation efforts have failed. It would be a very worrying precedent if conservationists abandoned the ideals of optimal habitat and self-sustaining wild populations and settled instead for a world in which populations were maintained in sub-optimal conditions only by constant restocking from captive sources, rather like some of the populations of pheasants maintained for shooting. For this reason, the Royal Society for the Protection of Birds and the government-sponsored Joint Nature Conservation Committee oppose captive rearing and release as a conservation technique for barn owls, except where releases are part of a structured experiment designed to test the conservation value of the technique. Such experiments need a detailed survey of the wild population, a complete habitat survey, and the identification of the reasons for the bird’s depleted status before any captive-bred birds are released. It is also crucial to mark all released birds to track their progress.
One proposal that would immediately discourage casual operators, and which would, at the same time, introduce some much-needed statutory control, is adding the barn owl to Schedule 9, Part 1, of the Wildlife and Countryside Act, 1981, in mainland Britain and Schedule 9, Part 1 of the Wildlife Order (1985) in Northern Ireland. In Britain, the Department of the Environment has consulted on The Wildlife and Countryside Act, following a recommendation from the then Nature Conservancy Council, and are now considering these proposals.
Such changes to the legislation would make it an offence to release barn owls, except under licence, or to allow them to escape into the wild. But for this measure to be fully effective, the barn owl should also be removed from Schedule 3 of the Act and included in Schedule 4, which lists ‘birds which must be registered and ringed if kept in captivity’. Under the present Schedule 3 listing, only barn owls offered for sale have to be close-ringed. Schedule 4 status would almost certainly reduce substantially the number of barn owls for sale. More-over, the introduction of registration – and, importantly, registration charges – would deter casual keepers from the indiscriminate release of young barn owls into the wild where their chances of surviving to breed are extremely low.
John Cayford is a research biologist with the Royal Society for the Protection of Birds and is presently researching barn owls in East Anglia.
Steve Percival conducted the British Trust for Ornithology research into the population dynamics of British owls and is now a lecturer at Sunderland Polytechnic. The views expressed in this article are those of the authors and not necessarily those of the organisations they represent.