MODELING THE RELATIONSHIP BETWEEN BIRD POPULATION VARIABLES AND HEDGEROW, AND OTHER FIELD MARGIN ATTRIBUTES .2. ABUNDANCE OF INDIVIDUAL-SPECIES AND OF GROUPS OF SIMILAR SPECIES

1. An earlier paper related bird species richness to hedgerows and oth er field boundary attributes including adjacent land use. The study wa s over several years (winter and summer) at two sites, Huntingdon and Swavesey, in East Anglia UK. 2. The present paper deals with similar r elationships, but the bird variables used are the abundance of individ ual species, of groups of species (all finches, all raptors, etc.) and of all birds, as well as Simpson's index of diversity. This required extensive modelling - 105 models for Huntingdon and 174 for Swavesey. 3. The results of all 279 models are presented in a condensed form, hi ghlighting the importance of given field boundary attributes to partic ular species or groups of species. 4. Like bird species richness in th e earlier paper, the abundance of many species was strongly influenced by the land use, and by the main vegetation variables (tree height an d number, hedgerow length, height and width). Land use was important t o a larger majority of species, the exceptions being carrion crow, phe asant, reed bunting and wren. 5. Verge width appeared important for sm all insectivores (blue tit) and was particularly important for seed ea ting birds, e.g. most finches and buntings, red-legged partridge in su mmer, and carrion crow and skylark in winter. 6. Ditch dimensions were associated with the abundance of some seed eaters (linnet, reed bunti ng and goldfinch) and insectivores (blackbird, great tit, skylark, son g thrush and wren). Kestrel and the groups raptors, corvids, waders an d aquatics were associated with large ditches. 7. Though the general m anagement prescriptions to benefit the majority of farmland birds were found to be similar to those in the earlier paper, the detailed speci es specific modelling made it possible to examine the habitat requirem ents of particular species. 8. Ecological evaluation of the results fr om the two studies are presented in a form considered to be of value f or practical management. Bird species and groups of birds are categori sed with respect to their likely requirements of particular attributes of the field boundaries.