Modelling the Relationship Between Bird Population Variables and Hedgerow and Other Field Margin Attributes. I. Species Richness of Winter, Summer and Breeding Birds

Abstract

1. An understanding of how farming practices in adjacent fields and the dimensions of the hedge and other components of the boundary affect birds is essential for efficient conservation management of field boundaries. This paper is based upon surveys of field boundary transects at two sites in eastern England. 2. The first study, near Huntingdon (1983-85), was based upon a range of field boundaries, from small ditches to tall hedges. The boundaries were between small pasture, small arable 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 Great Ouse. This study also included a range of drainage regimes. 4. Regression models were used to relate measures of bird species richness, in both winter and summer over several years, to field boundary attributes, including adjacent land use. 5. Bird variables were positively correlated with the physical size of the hedge, the number and height of trees and adjacent permanent pasture. These attributes accounted for most of the observed variation in bird variables. Ditch and verge dimensions played a statistically significant but relatively less important role. 6. Field boundary management options, beneficial for bird conservation with relatively little agricultural cost, are presented.