Farmland conservation in West Africa: how do hedgerow characteristics affect bird species richness?

Abstract

Capsule The value of farmland for birds at a site in Nigeria, West Africa, was highly dependent upon the habitat structure, with wider and more continuous hedges supporting more bird species. Aim To understand the value of hedges in Nigerian farmland to bird species richness. Methods We used line transects to survey birds and vegetation on 166 systematically selected hedgerows on fallow, cultivated and harvested fields in Jos East, Nigeria. Results Wider hedges supported higher species richness. Plant species composition was a weak predictor of bird species richness compared to hedge width. There was no observed difference in distribution of bird richness across field types, suggesting that the value of hedgerows for biodiversity is comparable, regardless of farming method. Continuous hedgerows (hedgerows with vegetation gap < 1.5 m) held higher species richness compared with discontinuous (hedgerows with vegetation gap > 1.5 m) hedges. Conclusion This result suggests that hedge size and structure, rather than plant species composition, is an important predictor of avian species richness in hedgerows surrounding farmland. Therefore, the value of farmland for birds in this part of Africa is highly dependent upon the habitat structure, with wider and more continuous hedges supporting more bird species.