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Home , Barnacle goose, Species reintroduction

Review of status and categorisation of feral on the British List

Keith Vinicombe, John Marchant and Alan Knox, on behalf of the British Ornithologists' Union Records Committee

he principal task of the BOU Records Committee is to maintain the list Tof and subspecies which have occurred in Britain and . This work involves not only the assessment of records of birds potentially new to Britain, but also monitoring the status of all species to ensure that categori­ sations remain appropriate. Categorisation was introduced in 1971 to indicate those species for which there were no recent records (category B) and those whose breeding had originally been introduced, accidentally or on purpose, by man (category C). Species which have been recorded in an appar­ ently wild state at least once since 1st January 1958 arc placed in category A, which forms the bulk of the British and Irish List (BOU 1971, 1992a). Categorisation has brought its own difficulties in that the allocation of species to one category or another sometimes relics on fragmentary evidence and may depend on the subjective views of Committee members. For some species, more than one category is appropriate. One group which presents problems of categorisation comprises those species which occur fcrally. In the fifth and sixth editions of the BOU's check­ list of the birds of Britain and Ireland (BOU 1971, 1992b), four species were judged to have fallen into two categories and were given dual status. Three of these (Mute Swan Cygnus olor, wiser and Goose canadensis) were categorised AC because both wild and introduced birds occur or form the basis of our breeding populations. Capcrcaillie Tetrao urogal- his was categorised BC because the current introduced replaced a wild one which died out in the eighteenth century. This paper discusses the results of a review by the BOURC of the status and categorisation of feral species in Britain (BOU 1993). The origins of the

[Bril. Birds 86: 605-614, December 1993] 605 606 Status and categorisation of feral birds review lay in Committee discussions of the sixth checklist (BOU 1992b), fuelled by new information particularly from two important surveys: the Wild­ fowl & Wetlands Trust's 'Introduced Goose Survey' (IGS) in the summer of 1991 (Delany 1993) and the British Trust for Ornithology's New Atlas of Breed­ ing Birds in Britain and Ireland: 1988-1991 (Gibbons et al. 1993, referred to below as the 1988-91 Atlas). The review has led to the dualling of categories for several further species, to indicate cither AC or AD4 status, and the addition of others for the first time to category D4. The latter, a subgroup of category D, consists of species that would otherwise appear in Category C except that their feral populations may or may not be self-supporting. Category D4, like the rest of category D, is very much a 'wait-and-see' holding category and docs not form part of the main British and Irish List. During the course of the review, the Committee considered what consti­ tuted a viable self-supporting feral population, fulfilling the qualification for category C. It was agreed that rigid rules should not be applied. There was clearly a difference between, for example, one concentrated breeding popula­ tion of 900 Egyptian Geese Abpochen aegpptiams in East Anglia and a widely scattered population of 900 Geese Branta leucopsis with sporadic and isolated breeding attempts. Also, the required population size would be differ­ ent for different species: 160 scattered Snow Geese Anser caerulescens may not be sell-sustaining, whereas 20 pairs of White-tailed Eagles Haliaeetm albicilla in could be. The populations of many feral species are dynamic: most of the scarcer ones can be expected to increase and perhaps qualify for higher categories in future years. In several cases, recategorisation arose from neither a change in status nor new information, but from new views within the Committee about how the categories should be implemented. For example, there have been no changes for decades in the status of feral Mallards Anas pkityrhymhos and Rock Doves (kdumha livia in Britain. Rather, it is the opinion of the Committee that these and other substantial feral populations deserve recognition and should not be ignored in faunal listings, whether at national or local levels.

Species recategorised Pink-footed Goose Anser bmchyrhynchus The IGS (Delany 1993) found 88 at 29 sites. Some of these may have been non-returning winter- visitors. One pair in Lancashire had seven young. The 1988-91 Alias recorded breeding in two 10-km squares and summering in an additional 14. The Rare Breeding Birds Panel recorded two summer records in the UK in 1990 (Spencer et al. 1993). Clearly, this is a species not yet estab­ lished and not qualifying for category 0, but the Committee decided that it marginally justified dual AIM status to encourage further monitoring.

Snow Goose A. caemltscem The IGS (bund 182 Snow Geese at 27 sites and at least 12% of those aged were juveniles. Since that survey, the Wildfowl ik Wetlands Trust has grounded 22 free-flying Snow Geese at Slim- bridge, Gloucestershire (Dr M. Owen in litl.}. In 1992, tire British feral population was estimated at 252, with 60 on Mull and Coll, Strathclyde (Evans 1993a). Feral breeding has been reported in a number of places and the population may be self-sustain­ ing (S. Delany in litl., Dr M. A. Ogilvie in litl). The 1988-91 Atlas, however, recorded breeding in only one square and summering in a further ten. The Committee considered that the population may at present be too widely scattered to be Status and categorisation offered birds 607 regarded as fully self-sustaining, and the species was given dual AIM rather than AC status. As with other category assignments, this will be reviewed from time to time.

Bar-headed Goose A. indicus The IGS discovered 85, the highest counts being of 19 mine young) at Slraliield Save in Hamp­ shire and 11 at Highiieid I^ake, South . The 1988-91 Atlas records breeding in one square and summering in three more. A pair produced two young in Greater Manchester in 1992 (Mrs A.J. Smith in till). Clearly, the species is not established, but numbers are likely to increase, so the species was added to category D4 to encourage monitoring.

Barnacle Goose Branla kumpsis The IGS found a total of 925 summering at 89 sites scattered throughout Britain. The largest flock was of 180 privately owned individuals at Seaview Marsh, Isle of Wight. Oflhose aged, 9% were juveniles, but, if the privately owned flocks are excluded (see below), this ligure rises to 17%. Breeding was noted at 15 sites. This figure of 925 is on a par with the 906 Kgyptian Geese found, and that species has, of course, been in category C since 1971. Barnacle Goose, however, differs in that the population is more widely scattered and 238 were based on three Wildfowl & Wet­ lands Trust reserves, at Slimbridgc, Gloucestershire, , Co. Durham, and Arundel, West Sussex. If these and the Isle of Wight flock are taken out of the total, then the 'feral' popula­ tion becomes 507. The Wiklfowi & Wetlands Trust is aetivelv diminishing its stocks of Barnacle Geese by reducing their breeding success, in some years to nil (Dr M, Oven in till). The 1988-91 Atlas found breeding Barnacle Geese in 17 10-km squares from Hampshire to Northern Ireland and Jura, Strathelyde, in comparison with just two squares in the 1968-72 Atlas (Sharrock 1976). The 1988-91 Atlas notes that this species is 'probably still too scattered for there to be a self-sustaining feral population. If the current increase in breeding records continues, how­ ever, there seems to be no reason to doubt that such a population could become established/ It is also considered that the 1988-91 Atlas map under-represents the range in Britain. Simon Dclany {in lilt.) considers that the Barnacle Goose population is now probably Viable and self-supporting1. Clearly, the species is at least borderline. The Committee decided to exercise caution and con­ sidered thai the population may currently be too scattered to warrant dual category AC status, but there can be little doubt that, unless control measures are taken, the population will continue to increase and it will not be long before AC status may be justified. The species is, therefore, given dual AD4 status, but the position will be reviewed periodically.

Muscovy Duck Cairma meschata A feral population of Muscovy Ducks has been present on the River Ouse at PJy, Cam­ bridgeshire, since the early 1980s (1988-91 Atlas). Broods were first noticed in 1987, and in November 1991 the population was estimated at approximately 130 individuals, of which about 60% were thai year's juveniles. The 1988-91 Atlas recorded breeding in four 10-km squares in Britain and summering in one other. The Committee considered that the popula­ tion is too recent to be added to category C, but this species obviously should be monitored. The species was therelbre added lo category D4.

Gadwall Anas strepem Fox (1988) confirmed that 'there is no doubt that the present Gadwall breeding population in Britain derives largely from introduced stock'. The breeding population has been estimated at 770 pairs in Britain and 30 in Ireland (Gibbons el al. 1993). The winter population reached 7,700 in 1991/92 (Cranswick A al. 1992). In view of the size of this population, dual AC status is clearly overdue.

Mallard A. plalyrkynckas The 1971 BOU checklist acknowledged that 'artificial rearing and re-stocking is widely practised' (BOU 1971). Aside from the wild-type birds which are introduced annually for shooting purposes, domesticated forms of the species are abundant feral breeders, particularly in amenity parks and on other waters close to human habitation. This species has also been given dual AC status. 608 Status and categorisation of feral birds Red-crested Pochard Netta rufina Isolated breeding occurred in Lincolnshire in 1937, in in 1968 and, since 1968, one or two pairs have nested in Britain in most years, chiefly in southern (Baatsen 1990), There is, however, a significant feral population of unknown origin at the Cotswold Water Park, Glouces­ tershire/Wiltshire, which has been established for some years. The Red-crested Pochard was first recorded at the Cotswold Water Park in January 1960, but became much more frequent during the 1970s. The first breeding occurred in 1975 (Mardle & Ogilvie 1976). In the late 1970s and early 1980s, the number of breeding attempts seems to have been limited by a shortage of females, but, by 1990, there were as many as ten cases. Breeding success has also been affected by pike Esox lucius (Baatsen 1990). Details extracted from the Gloucestershire Reports (1975-91) and from Evans (1993a) are given in table 1. Baatsen believes that the population has become self-sustaining and should continue to increase exponentially.

Table 1. Number of Red-crested Pochards Netta rufina at the Cotswold Water Park, Gloucestershire/Wiltshire, 1975-92

Year 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92

Maximum counts 6 7 11 13 15 14 13 16 11 24 18 17 22 25 35 26 34 45 No. of broods 1 1 1 0 1 1 0 0 0 0 1 ? 1 3 2 0 2 5

In the 1986 Gloucestershire Bird Report it is mentioned that a small, resident, free-flying population of about 15 individuals occurs in and around the Wildfowl & Wetlands Trust grounds at Slirn- bridge. Dr M. Owen (in lilt) believes that these birds did not originate from Slimbridge. The col­ lection attracts feral wildfowl from elsewhere and there have been no escape's of this species from Slimbridge for at least ten years. In addition, the species appeared at Bourton Pits, Gloucester­ shire, in 1974, with single broods in 1976 and 1981. Numbers there reached 12 in November 1981, but few have occurred since. The species also nested at Frampton-on-Severn, Gloucester­ shire, in several years during 1964-78, but fledging success was poor, probably because of preda- tion by pike (Mardle & Ogilvie 1976). This is another species that needs monitoring, but the Committee considers that the feral popu­ lation is not yet large enough to warrant dual AC status. The species has been given dual AD4 categorisation.

White-tailed Eagle Halimetus albicitla The reintroduction programme in western Scotland is showing clear signs of being successful. Totals of 39 males and 43 females were released on Rhum during 1975-85. Successful breeding began in 1985 and, by 1990, 15 young had been raised (Pienkowski & Love 1991). Although only- two young were reared in 1990, these were from nine separate breeding attempts (Spencer et at. 1993). Four pairs raised seven young in 1991 (Birds Magazine Winter 1991) and seven pairs laid eggs in 1992, resulting in four pairs rearing seven young, two of which are known to have died during the following winter (C. Crooke verbally). The Committee considers that this species is not yet firmly established, but the situation will be monitored. The species has been given dual AD4 status.

Northern Goshawk Accipiter genlilii Marquiss & Newton (1982) stated that 'Goshawks currently breeding in Britain are apparently not derived from Continental immigrants, but rather from birds which have escaped from falconers or been deliberately introduced.' According to Spencer el al. (1993), the current British population is probably about 200-300 pairs. The population is believed to be self- sustaining and the species has been afforded dual AC status.

Red Kite Milvus minus This species is currently being reintroduced into Scotland and England (Pienkowski & Evans 1991). A total of 122 was released during 1989-92, and nine young were raised in England and one in Scotland in 1992 (Evans & Stowe 1993). Obviously, this reintroduction attempt is still in its early stages, but the position will be monitored from time to time. The species has been given dual AD4 status. Status and categorisation of feral birds 609

Chukar Partridge Alectons chukar Chukars have been released in this country since 1970, although a few escapes from had been seen as early as 1968. An average of 2,700 Chukars per year were released until the early 1980s. They have also been crossed with the Red-legged Partridge A. rufa to produce a more pro­ ductive and easily reared gamebird. These hybrids were also widely released from as early as 1972. Most hybrids seen in the field were released individuals, rather than hybrids produced in the wild (Potts 1989). The release of non-indigenous species was prohibited by Section 14 of the Wildlife and Coun­ tryside Act 1981, but a general licence was issued in 1984 authorising the continued release of Chukars and Chukar X Red-logged Partridge hybrids. This licence was issued to allow game- farmers a sufficient period of time to phase out the release of both Chukars and their hybrids (Wilkinson 1987). From the end of 1992, it has not been legal to release them. Chukars and their hybrids are far less successful in the wild than pure Red-legged Partridges. On a farm in Sussex, the latter were producing young (to the age of six weeks) at 4.5 times the rate of Chukars or hybrids (Potts 1989). It is hoped that the revocation of the release licence will lead to the gradual disappearance of the Chukar and its hybrids. In view of the current uncer­ tainty, the Committee decided to place Chukar in category' D4 to encourage monitoring.

Grey Partridge Perdix perdix Earlier this century, Grey Partridges from , Hungary and were released in Britain and interbred with native ones to the extent that the population was considered no longer assignable to any particular race (Meinertzhagen 1952; BOU 1965). Studies of recent introductions of Grey Partridges have shown that the released birds fare less well in the wild than do native ones, as game-farms have selected birds for many generations, mainly for their egg production. This has reduced their success in the wild, so that released birds have had very little direct impact on the wild population (Dr G. R. Potts in litL). Nevertheless, in view of the fact that releases have been taking place for a considerable length of time and that integration of released and wild birds has occurred, the Committee has decided to assign this species dual AC status. Irish Grey Partridges are considered to be of wild origin (Dr G. R. Potts in lilt.).

Rock Dove (jrfumba livia The large feral populations of this species on our cliffs and in our cities make this an obvious can­ didate for joint AC categorisation. It seems surprising that the 'Feral Pigeon1 has been for so long ignored as a British bird.* The recognition of individuals that are truly feral is hampered by the regular appearance in the; wild of racing pigeons and other dovecote pigeons living in or newly absconded from semicaptivky.

Barn Owl Tyto alba From the early 1970s, this species has been the subject of numerous reintroduction attempts. The Department of the Environment (1993) estimated that between 2,000 and 3,000 have been re­ leased annually in recent years. Non-native races have also been involved. Since 25th November 1992, the Barn Owl has been placed on Schedule 9 of the Wildlife and Countryside Act 1981 and, since 1st January 1993, a licence has been required for its release. As a result of poor prac­ tices, a large proportion of those released were not surviving and the JNCC takes the view that there is no scientific case for the species' reintroduction (Dr C. A. Galbraith in litL). It is likely that only a small number of well-run schemes have resulted in feral breeding (R. F. Porter in lilt.) and that unco-ordinated releases will now be reduced. For these reasons, the Committee decided to give the species dual AD4 (rather than AC) status.

Other species considered The following species were also considered by the Committee, but no change of category was considered necessary.

*It was not ignored by the BTO/Irish Wildbird Conservancy atlas projects, being included in both the 1968-72 Breeding Atlas (Sharrock 1976) and the 1981/82-1983/84 Winter Atlas (Lack 1986). EDS 610 Status and categorisation of feral birds Night Heron .Nyiiiwrax nyvtkorax The Committee is aware that, semicaptive Night Herons are allowed to fly freely and to nest in a ! state at Edinburgh and at a site in Norfolk. Those at Edinburgh are. believed to belong to the American race hoactli. Adults and juveniles from these sites, some unringed, are difficult or impossible to separate from wild birds visiting Britain from abroad (see Rogers el at. 1993). There is, however, no indication as yet that a true feral breeding population will develop beyond the present sites. The Committee would welcome, information on the feral status of this species.

Whooper Swan Cygmm cygnm The species is at large in small numbers in the feral state (for example, up to three at Bhtnham, Bedfordshire, since at least 1983, where a pair hatched but failed to rear young in 1993) and it occasionally breeds in Scotland in an apparently wild state. Between 1979 and 1992, up to two feral pairs have nested almost annually in the Endrick Marshes, Lorh Lomond, Strathclyde. The swans originated from a local wildfowl collection which closed down. In their ten successful sea­ sons, 34 cygnets hatched, of which 21 fledged, but they appear to have been assimilated into the wild wintering populations (Mitchell 1993). In view of the tenuous nature of this feral population and the possibility that it may not survive the deaths of the remaining escaped adults, the Com­ mittee decided not to give the species dual AD4 categorisation.

White-fronted Goose Ansa albijrons The 1GS found 77, including 40 in Norfolk and 23 of the race ftmtimsiris (including three juveniles) on , Strathclyde. On May, lull-winged feral individuals originate from a small wildfowl collection on the island and two to five pairs have bred every year since at least 1986. It seems likely that the population has not increased because the young arc assimilated into the wild wintering population (Dr M, A. Ogilvie in lit/..). The only evidence of breeding in England was three juveniles at Hardley Flood, Norfolk. Clearly, this is a species that does not have a viable self-supporting population and, in view of the fact that its breeding attempts seem at present to be sporadic and irregular, the Committee decided not to add to its current category A status.

Lesser White-fronted Goose A. mlhmpm The IGS Ibund 29, including 24 in East Anglia, where a flock of 15 full-winged individuals is kept at The Otter Trust near Bungay, Suffolk. On this basis, there is no real leral population in Britain. There is, however, a complication with this species. Two reintroduction programmes are taking place in Scandinavia, one in and one in (Paynler 1991), In Finland, groups of young Lesser Whitefroms are being released in Lapland (eight in 1989 and 27 in 1990) and these are being fitted with blue neckbands. One of these, released on 3rd July 1990 (Evans 1992), has been recorded at Slimbridge (and in Dyfed), with the wild White-fronted Geese, in the three winters 1990/91-1992/93. In Sweden, Lesser Whitefroms are being reared under Barnacle Geese. It is hoped that the foster parents will lead the Lesser Whilcfronts to set up a new winter­ ing area in the . These birds are being colour-ringed. One- a first-winter -occurred in Lancashire in winter 1991/92 and was reported again in Clwyd in June 1993 (Rogers el at, 1993). It had been reared under Barnacle Geese at Stockholm Zoo and released in Swedish Lap­ land in July 1991 (Evans 1992). Released birds have already paired with wild Lesser Whitefronts and produced unringed young. The BOURC feels that it is now impossible to be certain that any Lesser Whitefront in Britain is truly wild. If the Scandinavian reintroduction projects restore the Lesser Whitefront population to a much higher level and it proves to be self-supporting, then con­ sideration will be given to dual AG status on the grounds that Britain is receiving individuals from an introduced population. It is too early to be sure that the programmes will be a success and the Committee decided that the species should be retained in category A, but its status will be re­ viewed from lime to time.

Other geese Other geese recorded in small numbers on the IGS were Bean Goose A, fabalis (32), r^mperor Goose A. mmiffta (14), Brent Goose B. bemkla (nine), Swan Goose A. cygnoicks (eight), Ross's Goose A. «».«;' (three) and Red-breasted Goose B. rujkottis (two). The numbers of these and other feral waterfowl were too small to warrant anv change in their categorisation or addition to category D4. Status and categorisation of feral birds 611

Ruddy Shelduck Tadarna Jemigmea The 1988-91 Atlas recorded breeding in one square and summering in four others, 'The species is observed frequently in Britain, particularly in late summer, but widely ignored on tile grounds that all are likely to be of captive origin. But might Britain be receiving Ruddy Shelducks from viable, self-supporting, feral Continental populations? The Committee's understanding of the situation is that, although the species does sometimes breed in the wild in the Netherlands and , the attempts are somewhat sporadic and no populations are fully self-supporting. This is a successtiil species in captivity, which produces large numbers of young. On the Continent, breeders tend to release excess young at the end of the breeding season, contributing to the late- summer peak of this species in Britain. The Committee decided that, in the absence of information to the contrary, the species should remain in category B.

Wood Duck Aix sponsa The 1968-72 Aflat recorded the presence of Wood Ducks in eleven 10-km squares. Breeding was coniirmed in nine of these, mostly in Surrey, where up to ten pairs nested regularly on a private estate at Puttenham, near Guildford. The 1988-91 Atlas shows six squares with confirmed breed­ ing (four in the Southeast and two in the West Midlands), together with presence in a further 24. The species shows a slight extension of range from the previous stronghold in Surrey and Berk­ shire inlo Sussex, Kent and parts of mainly southern East Anglia. Frost (19871 also recorded three breeding records in in 1984-86. In response to a BOURC request for information which was published in various journals and magazines, the Committee received just seven letters, six of which related to isolated, widely scat­ tered sightings. Evans (1993b) also collected records of the species during 1990-91 and listed a maximum of 57 individuals, with breeding attempts at Tunstall Park, Staffordshire (pair with live young on 30th June 1990), and at Bough Beech Reservoir, Kent (female laid infertile eggs in 1990). Most records came from the Home Counties, southeast England and the Midlands, with some north to Cheshire, Lancashire and Derbyshire. In view of the small numbers at large arid the paucity of breeding attempts, there is no justification for upgrading this species from eategoi'y Dl.

Established category C species The following species are well established and eurrendy in category C, AC or BC. Their status was not reviewed as no changes have taken place to justify recategorisation: Mute Swan, Greylag Goose, , Egyptian Goose, Mandarin Duck Aix gakriculaki, Ruddy Duck Oxvura jamaimisis, Capercaillie, Red-legged Partridge, Common Pheasant Phasianus roltiium. Golden Pheasant Chyysolophus pictm, Lady Amherst's Pheasant C. amhmtiae, Rose-ringed Parakeet Psittacula krameri and Little Owl Athene rmtua.

Repercussions of creeping naturalisation The Committee is very troubled about the apparent naturalisation or possible future naturalisation of increasing numbers of species, particularly wildfowl. The consequences of introductions in any country have rarely proved to be beneficial. The Committee believes that the present legislation and the mechan­ ism of its enforcement should be reviewed as a matter of urgency. Since many of the species are so mobile, potential problems are not neces­ sarily confined to the country of origin. Ruddy Ducks probably originating from collections in Britain had by 1992 been recorded in 15 European coun­ tries, and the Ukraine; the winter population is already more than 3,500 and increasing rapidly. The species has recently been the subject of con­ troversy following allegations that it poses a serious threat through competition and hybridisation to all populations of the globally threatened White-headed Duck 0. kucocephala, of which only 19,000 are believed to remain (Hughes & 612 Status and categorisation of feral birds Grussu in press). A similar situation may lx; developing with flamingos Phoeni- coplerus: escapes of various taxa arc beginning to breed in northwest (Trecp 1991) and may present a threat to the Mediterranean population of tire Greater Flamingo P. ruber roseus. Under Section 14 (1) of the Wildlife and Countryside Act 1981, it is an offence to release or allow to escape any which is not ordinarily resident in and is not a regular visitor to in a wild state or which is included in Part 1 of Schedule 9 of the Act (this is a list of which arc established in the wild). There is a case for reviewing Schedule 9 in the light of the Committee's work and adding those category C and 1)4 species not already on the Schedule. The Department of the Environment should also review education and enforcement regarding Section 14, as escapes and introductions arc occurring despite the legislation (R. F. Porter & G. Williams in till).

The need for monitoring Further monitoring of all the species covered in this paper is considered essen­ tial to determine future trends. A scheme to record escapes and feral birds is currently being set up by Mike Rogers under the auspices of die newly formed Association of County Recorders and Editors (ACRE). This will col­ late data nationally through the recorders' network. The BOURC is repre­ sented on the group steering the project. It is hoped that the scheme will lead to better information not only on feral species, but also for determining the patterns of occurrence of known escaped birds. The latter will help to inform those making assessments of possible natural vagrants. The Records Committee urges birdwatchers to submit records of all feral and escaped species to their local recorders and urges local-bird-rcport editors and committees to collect and disseminate this information. Records of cate­ gory D species and escapes should be published, preferably in an appendix to the main systematic list. The Rare Breeding Birds Panel is requested to con­ sider the nationwide monitoring of the breeding of rare feral and escaped birds. Escaped and feral species have been ignored for too long. Only with such efforts will useful data be gathered to assess their impact on the native avifauna and the countryside. The Records Committee would be pleased to receive information or copies of publications relating to feral and escaped species for use in future reviews. These may be sent to the British Ornithologists' Union Records Committee, c/o The Natural History Museum, Akcman Street, Tring, Hertfordshire HP23 6AP.

Acknowledgments The BOURC. is grateful to the following tor help during the course of this review: Colin Crooke, Ian Dawson, Richard Porter and Gwyn Williams at the RSPB, Simon Delany and Dr Myrfyn Owen at the Wildfowl & Wetlands Trust, Dr David Gibbons and the BTO for providing unpublished information from the 1988-91 Atlas, and Dr G. R. Potts, Director General of the Game Conservancy Trust. It is also grateful to the following for providing information: Sally Adams, Richard Andrews, Gordon Avery, Lee Evans, G, Fogg, Roy Frost, Andy Leggatt, Peter Martin, Graham Megson, Andy Middlcton, John Mitchell, K. R. Mudd, Dave Prycc and Mrs A. J. Smith. The following made useful comments on the manuscript: Dr Colin Galbraith on behalf of the JNCC, Dr Jeremy Greenwood on behalf of the BTO, Dr Malcolm Ogilvie on Status and categorisation of feral birds 613 behalf of the Rare Breeding Birds Panel, Dr Myrfyn Owen on behalf of the Wildfowl & Wetlands Trust, Dr G. R. Potts on behalf of the Game Conservancy Trust, and Richard Porter and Gwyn Williams on behalf of the RSPB.

Summary The British Ornithologists' Union Records Committee has reviewed the categorisation of species on the British list which have developed or have started to develop feral breeding populations. Significant proportions of the breeding populations of Gadwall Anas strepem, Mallard A. platyrhyn- elms, Northern Goshawk Accipiter gentilis, Grey Partridge Perdix perdix and Rock Dove Columba livia are derived from introduced or escaped stock, and these five species are now given dual category AC status. The following seven species, as well as occurring in a wild state, are also breeding ferally. Their numbers are such that their feral populations may not be self-supporting. They have been given dual category AD4 status: Pink-footed Goose Anser braehyrkynchus, Snow- Goose A. caerukscens, Barnacle Goose Branta kmopsis, Red-crested Pochard .Netta rufina, White-tailed Eagle Haiiaeftus albkilla. Mibus milvus and Barn Owl Tyto aiba. Three remaining species have been added to category D4: Bar-headed Goose Anser indicus, Muscovy Duck Cairina moschata and Chukar Partridge Akctoris clmkar. The Committee also considered a number of other species, but decided that their status should remain unchanged. Careful and systematic monitoring of these species, as well as all other feral and escaped birds, is urged. The Committee is deeply concerned at the creeping naturalisation of the species involved and recommends an urgent review of the relevant legislation and its enforcement.

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Keith Vinkombe, 11 Kennington Avenue, Bishopston, Bristol BS7 9EU John Marchant, British Trust for Ornithology, The National Centre for Ornithology, The Nunnery, Thetford, Norfolk IP24 2PU Dr Alan Knox, Buckinghamshire County Museum, Tring Road, Halion, Buckinghamshire HP22 5PJ