Abstract from BTO Research Report No 136:

Marchant, J.H. & Gregory, R.D. (2006)

Population changes of certain opportunistic bird species in the United Kingdom between 1985 and 1994.
ISBN: 1-904870-60-0

Executive Summary

Population trends of Woodpigeon Columba palumbus, Collared Dove Streptopelia decaocto, Jay Garrulus glandarius, Magpie Pica pica, Jackdaw Corvus monedula, Rook C. frugilegus, Carrion Crow C. corone, Starling Sturnus vulgaris and House Sparrow Passer domesticus were examined over the period 1985 to 1994 using data from the Common Birds Census. Substantial increases were found for Carrion Crow, Woodpigeon and Collared Dove, and decreases for Starling and House Sparrow. Our results are discussed in the context of the long-term changes in bird populations that have been reported since the start of this century. The status of seven of the species is secure, but we recommend Conservation Vigilance for Starling and House Sparrow.

1. INTRODUCTION

The Wildlife and Countryside Act (1981) listed thirteen opportunistic bird species, Lesser Black-backed Gull Larus fuscus, Herring Gull L. argentatus, Great Black-backed Gull L. marinus, Feral Pigeon Columba livia, Woodpigeon C. palumbus, Collared Dove Streptopelia decaocto, Jay Garrulus glandarius, Magpie Pica pica, Jackdaw Corvus monedula, Rook C. frugilegus, Carrion Crow C. corone, Starling Sturnus vulgaris and House Sparrow Passer domesticus, under Schedule 2, Part II. Under this legislation as originally enacted, birds of all these species could be controlled at any time. All species have recently been removed from that schedule, to bring Great Britain into line with the requirements of the European Community for the protection of all wild birds. However, the United Kingdom Government has secured a derogation in respect of these thirteen species under Article 9 of the European Directive on the Conservation of Wild Birds (EC/79/409). Since January 1993 a licensing system has been in operation by which the UK Government can issue a general licence, under section 16 of the Wildlife and Countryside Act, for the taking of these species in the interests of health and safety or to prevent serious damage to livestock and crops, or for the protection of flora and fauna. The derogation entails a responsibility to monitor these species to provide data that indicate their population levels and trends.

The population levels of these opportunistic species are of special interest to birdwatchers and conservationists alike. In particular, several of the corvids have shown long-term changes in population status (Parslow 1973, Marchant et al. 1990). Magpie, and to a lesser extent Carrion Crow, are important predators of eggs and nestlings (Potts 1986, Gooch et al. 1991, Groom 1993). It has been suggested that their population increases may have been a cause of parallel declines of open-nesting species, although there is little direct support for this (Potts 1986, Gooch et al. 1991, Groom 1993). All thirteen species are familiar and widespread birds whose interests sometimes conflict with those of man. There is therefore considerable value in monitoring their status as ‘pest species'.

The Common Birds Census (CBC), operated by the British Trust for Ornithology since 1962, is the only source of data on trends in breeding population for the period and species included in this study (Marchant et al. 1990). Most CBC plots are on farmland or in woodland; the data are used to monitor population changes and study fine-scale distribution patterns among birds, particularly in these two types of habitat. Standard reporting of population change covers farmland and woodland, combining plots throughout the United Kingdom; a small number of scarcer species are monitored by combining data from all habitat types. More than thirty years' data on United Kingdom bird populations are now available.

The CBC forms an invaluable resource for the study of population changes in around 75 bird species. Species for which the CBC can monitor population levels are generally the commonest and most widespread British birds. Among the species previously in Schedule 2, Part II, the gulls and Feral Pigeon, though all with large breeding populations in the United Kingdom, are too scarce in the habitats surveyed by the CBC for monitoring to be possible. Rook, although both numerous and widespread, has not routinely been indexed because of its highly clumped nesting distribution. Rooks are recorded as present during the breeding season on most CBC plots, but only active nests are counted for monitoring purposes. Nesting was reported on between 2% and 12% of plots in 1965-88 (Marchant et al. 1990), so that samples of plots available for population indexing have been relatively low. Total counts of nests on CBC plots have, however, been substantial in recent years and sufficient to indicate the population trend over the past decade.

The CBC data for the ten-year period 1985-94 are presented in this report for all of the terrestrial species formerly listed on Schedule 2, Part II, with the single exception of Feral Pigeon for which insufficient data were available. Feral Pigeon populations will be monitored as from 1994 by the new Breeding Bird Survey: the first results will be available after the 1995 survey.

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