MODELING THE RELATIONSHIP BETWEEN BIRD POPULATION VARIABLES AND HEDGEROW AND OTHER FIELD MARGIN ATTRIBUTES .1. SPECIES RICHNESS OF WINTER, SUMMER AND BREEDING BIRDS

1. An understanding of how farming practices in adjacent fields and th e dimensions of the hedge and other components of the boundary affect birds is essential for efficient conservation management of field boun daries. This paper is based upon surveys of field boundary transects a t two sites in eastern England. 2. The first study, near Huntingdon (1 983-85), was based upon a range of field boundaries, from small ditche s to tall hedges. The boundaries were between small pasture, small ara ble or large arable fields. 3. The second study, at Swavesey (1985-87) , covered the various permutations of boundary structure, and adjacent cropping, available within a catchment of a tributary of the River Gr eat Ouse. This study also included a range of drainage regimes. 4. Reg ression models were used to relate measures of bird species richness, in both winter and summer over several years, to field boundary attrib utes, including adjacent land use. 5. Bird variables were positively c orrelated with the physical size of the hedge, the number and height o f trees and adjacent permanent pasture. These attributes accounted for most of the observed variation in bird variables. Ditch and verge dim ensions played a statistically significant but relatively less importa nt role. 6. Field boundary management options, beneficial for bird con servation with relatively little agricultural cost, are presented.