Effects of crop diversity on bird species richness and abundance in a highland East African agricultural landscape

Ndang'ang'a, Paul K.; Njoroge, John B.M.; Ngamau, Kamau; Kariuki, Wariara; Atkinson, Philip W.; Vickery, Juliet A.

doi:10.2989/00306525.2013.775189

Cited by 3 publications

(2 citation statements)

References 28 publications

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“…Contrary to our hypothesis, we did not observe higher bird species richness in landscapes with diverse cropping systems, regardless of landscape context (low vs. high landscape heterogeneity), functional group or spatial scale considered. Therefore, we cannot confirm previous findings that birds in general or functional groups such as non-crop breeding farmland species in particular benefit from crop functional diversity [ 15 , 16 , 18 , 22 , 26 , 27 , 39 ].…”

Section: Discussioncontrasting

confidence: 69%

“…At the same time, crop diversity effects may not equally apply to all bird species, owing to different resource, habitat and nesting preferences of specific functional groups (i.e. species with shared characteristics or requirements), so that individual responses could be masked in whole community analysis [ 17 , 24 – 26 ]. Whether effects are found may also depend on the choice of crop diversity index (i.e.…”

Section: Introductionmentioning

confidence: 99%

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Landscape heterogeneity rather than crop diversity mediates bird diversity in agricultural landscapes

et al. 2018

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Crop diversification has been proposed as farm management tool that could mitigate the externalities of conventional farming while reducing productivity-biodiversity trade-offs. Yet evidence for the acclaimed biodiversity benefits of landscape-level crop diversity is ambiguous. Effects may strongly depend on spatial scale and the level of landscape heterogeneity (e.g. overall habitat diversity). At the same time, contrasting within-taxon responses obscure benefits to specific functional groups (i.e. species with shared characteristics or requirements) if studied at the community level. The objectives of this study were to 1) disentangle the relative effects of crop diversity and landscape heterogeneity on avian species richness across five spatial scales ranging from 250 to 3000 m radii around focal winter wheat fields; and 2) assess whether functional groups (feeding guild, conservation status, habitat preference, nesting behaviour) determine the strength and direction of responses to crop diversity and landscape heterogeneity. In central Germany, 14 landscapes were selected along independent gradients of crop diversity (annual arable crops) and landscape heterogeneity. Bird species richness in each landscape was estimated using four point counts throughout the breeding season. We found no effects of landscape-level crop diversity on bird richness and functional groups. Instead, landscape heterogeneity was strongly associated with increased total bird richness across all spatial scales. In particular, insect-feeding and non-farmland birds were favoured in heterogeneous landscapes, as were species not classified as endangered or vulnerable on the regional Red List. Crop-nesting farmland birds, however, were less species-rich in these landscapes. Accordingly, crop diversification may be less suitable for conserving avian diversity and associated ecosystem services (e.g. biological pest control), although confounding interactions with management intensity need yet to be confirmed. In contrast, enhancement of landscape heterogeneity by increasing perennial habitat diversity, reducing field sizes and the amount of cropland has the potential to benefit overall bird richness. Specialist farmland birds, however, may require more targeted management approaches.

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