Top‐Down Drivers of Savanna Ecosystems Promote Bird Foraging: Effects of Fire and Large Mammals on Granivorous and Insectivorous Birds

Fire and large mammal herbivores play major roles in shaping plant communities in savannas. However, the interactive effects of these drivers on other components of savanna biodiversity are less well understood. This study, conducted in Gorongosa National Park, Mozambique, tested the effects of fire and large mammals on the abundance and richness of foraging granivorous and insectivorous birds. We manipulated the presence of large mammals and early and late dry season burns and measured multiple aspects of grasses and woody plants as well as bird foraging. We modeled the abundance and richness of foraging birds in response to tree basal area, shrub abundance, grass biomass, grass cover, and grass richness in plots with and without large mammals and fire in the wet season prior to experimental burns, in the dry season following the burns, and in the subsequent wet season. Early and late dry season burns increased granivorous bird foraging in the wet season following the fires. Foraging insectivores increased in plots with cold burns 4 months after fire. The exclusion of large mammals generally reduced bird foraging, although positive effects of large mammal exclosures were detected when resources were limited, and fire and large mammals indirectly affected foraging by changing vegetation and therefore seed and arthropod food resources. Foraging was higher for both guilds where tree cover was greater, and foraging of insectivores increased with shrub cover and grass biomass and richness. These results emphasize the importance of considering fire‐herbivore interactions for the conservation of savanna biodiversity.