The requirement to avoid the introduction of non-native species is expressed in several Directives, Conventions and Agreements. The deliberate or accidental translocation of species beyond their native range has led to the loss of biodiversity throughout the world and economic damage to agriculture, forestry, aquaculture and other sectors. In the United States alone, economic damage caused by non-native species is estimated to have cost $97 billion. Within the UK Biodiversity Action Plan, non-native species in general are cited as threatening factors in 17 habitat action plans (23% of action plans) and 46 species action plans (12%). Effects include competition (62%), habitat loss or degradation (18%), predation (12%) and disease (8%). However, apart from largely anecdotal evidence, remarkably little is known about the effects of most non-native and re-established species (species native to Britain but that may have been released into the wild following local or national declines) on their wider environment. This is unsatisfactory as the monitoring of such species is arguably a requirement under international legislation.

The status of non-native waterbirds in the African-Eurasian Waterbird Agreement Area

The African-Eurasian Waterbird Agreement (AEWA) covers over 118 range states in Africa, Asia, Europe and the Middle East and aims to encourage the right conditions for the conservation and management of migratory waterbirds. As the presence and continued release of introduced species is detrimental to the meeting of this aim, the BTO was asked by AEWA and the UK Government to assess the scale of the problem in 1999 and to provide an update in 2007 (Blair et al. 2000; Banks et al. 2008). Both assessments were achieved by questionnaire surveys to Government and local ornithologists in each range state and by searching published and grey literature. The recent results were startling and the unexpected scale of the problem demonstrated clearly how little the issue had been researched. Thirty-two introduced species had been recorded as breeding more than five times in the AEWA region during the past 20 years. Twenty-seven introduced species had been recorded to breed fewer than five times and a further 45 waterbird species had been introduced but were not thought to have bred. Most introductions have occurred in northern and western Europe, with fewer in other parts of the AEWA range. The vast majority of introduced waterbird species are Anatidae; relatively few species from other waterbird families have established introduced populations. Many populations of introduced waterbird species had increased, and their ranges expanded, since 1999. There was a broad relationship between the wealth of a country and the existence of introduced waterbird species. The collection and captive breeding of birds associated with wealthier countries make it much more likely that accidental escapes or releases will occur.

The responses and the review identified two major benefits to introductions. Some can be of economic value by providing opportunities for human employment and as sources of food and sport. Introductions may also help ensure the conservation of relic populations of endangered species, but it is rare that the continued survival of a species can only be ensured by its release into a totally new habitat. These benefits are normally much outweighed by the costs of introductions. Introductions have led to the extinction of numerous species , contributed towards loss of genetic purity by hybridising with native species, led to local declines in the abundance of native species either through competition or (for at least one introduced waterbird species) predation of the eggs and young of native species, and caused economic and environmental damage. Whereas competition between species is a natural part of evolution, such competition should not be dependent on the intervention of humankind. Publications

The survey used a stratified approach to determine by how much the breeding populations of Greater Canada and re-established Greylag Geese had increased between 1988-91 and 2000. Survey results showed that Greater Canada Geese had increased by 166% (to about 90 000 adults) and Greylag Geese by 170% (to about 25 000 adults), average per annum rates of increase of 9.3% and 9.4%, respectively. Great Britain has seen no obvious decline in the rate of growth of these birds since the 1950s. There is a clear need to further understand the effects that these now very common species are having on native biodiversity. Publications

Little was known about the ecology of wild Golden Pheasants in their native China, where they are declining rapidly, and in their three other allegedly viable naturalised populations in Galloway, Sussex/Hampshire and East Anglia. Golden Pheasants were first recorded in captivity in Britain during the 1720s. Until the Wildlife and Countryside Act (1981) made it illegal to release the species into the wild, these birds were sufficiently frequently liberated to be admitted to the British and Irish List in 1971. The British population was estimated at between 1000-2000 individuals concentrated in Thetford Forest, the largest lowland commercial forest in England. A BTO study of radio-tagged individuals in Thetford Forest found that Golden Pheasants moved a maximum of 1250 m from one end of their home range to the other over a year, a short distance for such large birds. The home ranges measured over a whole year varied between 23.0 ha and 45.0 ha and were centred around young, dense, unbrashed plantations of Scots pine, Corsican pine and lodgepole pine planted since 1960-79. Such dense plantations may afford some protection from predators, and yet over half of the tagged birds fell prey to foxes.

In Thetford Forest, it is now unusual to see more than two or three individuals together, although up to 100 males were seen together during the 1950s. This decline is possibly occurring in its other British strongholds and the species is now thought to be extinct in Scotland. Its possible disappearance from Britain could be considered unfortunate as there is no evidence of it affecting native wildlife negatively and it is an attractive addition to our avifauna. Furthermore there is evidence that Golden Pheasants are declining in China and if this decline were to continue the species could become globally threatened; at that point a viable population in Britain would be considered valuable. Publications

Banks, A.N., Wright, L.J., Maclean, I.M.D. & Rehfisch, M.M. (2008) Review of the Status of Introduced Non-Native Waterbird Species in the Area of the African-Eurasian Waterbird Agreement: 2007 Update. British Trust for Ornithology Research Report, 489 to the AEWA Secretariat. British Trust for Ornithology, Thetford, UK.

Blair, M.J., McKay, H., Musgrove, A.J. & Rehfisch, M.M. (2000). Review of the status of introduced non-native waterbird species in the agreement area of the African-Eurasian Waterbird Agreement. British Trust for Ornithology Research Report 229 to the DETR. British Trust for Ornithology, Thetford, UK.

Rehfisch, M.M., Allan, J., Hughes, B., Rhymer, J., Robertson, P., Shaw, K.A. & Williams, M. (2006). Symposium 33 Competition and hybridization resulting from introduced waterbirds: an issue rising up the political agenda. Acta Zool. Sin., 52 (Suppl.), 570-571.

Rehfisch, M.M., Blair, M.J., McKay, H. & Musgrove, A.J. (2006). S33-1 The impact and status of introduced waterbirds in Africa, Asia Minor, Europe and the Middle East. Acta Zool. Sin., 52 (Suppl.), 572-575.

Surveys of Introduced and Re-established Geese

Austin, G.E., Rehfisch, M.M., Allan, J.R., Holloway, S.J. In press. Population size and differential population growth of Canada Branta canadensis and Greylag Goose Anser anser across habitats in Great Britain in the year 2000. Bird Study.

Rehfisch, M.M., Austin, G.E., Holloway, S.J., Allan, J.R. & O’Connell, M. (2002). An approach to the assessment of change in the numbers of Canada Branta canadensis and Greylag Geese Anser anser in Southern Britain. Bird Study, 49, 50-59.

The Behaviour of introduced Golden Pheasants

Balmer, D.E., Browne, S.J. & Rehfisch, M.M. (1996). A year in the life of Golden Pheasants Chrysolophus pictus L. In: The introduction and naturalisation of birds. ed. by J.S. Holmes & J.R. Simons, 87-93. London, HMSO.

Parish, D., Rehfisch, M.M. & Shaw, G. In press. Golden Pheasant Chrysolophus pictus. In: The Birds of Scotland. ed. by Forrester, R. & Andrews, I. SOC, Scotland.

Rehfisch, M.M. (1997). Golden Pheasant Chrysolophus pictus. In: The EBCC Atlas of European Breeding Birds: their distribution and abundance. ed. by E.J.M. Hagememeijer & M.J. Blair, 220. T & A D Poyser, London.