Predation drives nesting success in moist highland grasslands: the importance of maintaining vegetation cover for bird conservation §
By focusing on process-oriented data rather than inventory-type data, this study provides a robust understanding of the effects of agricultural management on grassland bird reproductive output in the moist highland grasslands (MHGs) of South Africa. Four-hundred and four nests of 12 grassland-breeding bird species were monitored in five different land-use types. Survivorship was modelled using Program MARK to assess the effects of these management practices on reproductive performance. Six of the species were modelled individually to assess speciesspecific responses. Both nest-site selection and nest success were driven by vegetation structure, which in turn is driven by habitat management. There was an increase in nesting success through the season for cup (ground) nesting birds as vegetation structural complexity increased through the breeding season (September to March). Nest success was driven by predation pressure rather than food availability. Analysis of the nesting success of the Yellow-breasted Pipit Anthus chloris indicated that unconserved areas house sink populations, confirmation of which would depend on a measure of adult survival. The generalist African Pipit Anthus cinnamomeus, on the other hand, thrived in disturbed, communally grazed lands. To conserve MHG bird species, managers should maintain a mosaic of burning regimes, with the majority burning biennially or less frequently.
Keywords: fire, grassland, grazing, nest success, pipit, predation