Conservation headlands: effects on butterfly distribution and behaviour.

Abstract

The gamebird management system known as Conservation Headlands, whereby the outermost 6 m of cereal fields are selectively sprayed, is known to affect the distribution and abundance of many non-game species including butterflies. Previous work on butterflies in the arable environment showed that more butterflies were found associated with field margins which had received reduced pesticide inputs, but only speculated on the mechanism which produced the enhanced numbers.
This study examines the differences in butterfly behaviour between field margins with conservation headlands and those sprayed according to normal farm practice. The results show distinct within-season differences in behaviour patterns. Spring emerging butterflies in field margins sprayed according to normal farm practice are principally associated with the field boundary habitat (the hedgerow), whilst those in fields with conservation headlands are principally associated with the headland. The proportion of time spent in flight, feeding, resting and mate location behaviours also changed with headland regime. In normally sprayed field margins the principal activity was flight, in field margins with conservation headlands this dominance was broken with striking increases in foraging activity on headland flora. Butterflies that emerged in the summer were less strongly associated with the headland than those that emerged in the spring. The discussion relates these differences to the changing nature of the flora of the field boundary and headlands over the season and the population structure of the species studied. The role of resource provisioning for non-target species in the arable environment, and the effect of resources on landscape permeability to dispersing individuals are also discussed.