Abstract
Large native mammals are declining dramatically in abundance across Africa, with strong impacts on both plant and animal community dynamics. However, the net effects of this large-scale loss in megafauna are poorly understood because responses by several ecologically important groups have not been assessed. We used a large-scale, replicated exclusion experiment in Kenya to investigate the impacts of different guilds of native and domestic large herbivores on the diversity and abundance of birds over a 2-year period. The exclusion of large herbivorous native mammals, including zebras (Equus burchelli), giraffes (Giraffa camelopardalis), elephants (Loxodonta africana), and buffalos (Syncerus caffer), increased the diversity of birds by 30%. Most of this effect was attributable to the absence of elephants and giraffes; these megaherbivores reduced both the canopy area of subdominant woody vegetation and the biomass of ground-dwelling arthropods, and both of these factors were good predictors of the diversity of birds. The canopy area of subdominant trees was positively correlated with the diversity of granivorous birds. The biomass of ground-dwelling arthropods was positively correlated with the diversity of insectivorous birds. Our results suggest that most native large herbivores are compatible with an abundant and diverse bird fauna, as are cattle if they are at a relatively low stocking rate. Future research should focus on determining the spatial arrangements and densities of megaherbivores that will optimize both megaherbivore abundance and bird diversity.
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Acknowledgments
We gratefully acknowledge the support and cooperation of the Ministry of Education of the Republic of Kenya and Kenyatta University. This research was supported by a National Science Foundation grant (DEB CAREER 0196177) to FK and by grants from the American Society of Mammalogists and the University at Albany Graduate Student Organization to DO. The KLEE plots were built and maintained with grants from the James Smithson Fund of the Smithsonian Institution (to Alan Smith), the National Geographic Society (4691-91), the National Science Foundation (BSR-97-07477 & BSR-03-16402), and the African Elephant Program of the U.S. Fish and Wildlife Service (98210-0G563) (to TPY). Logistical support was provided by the Mpala Research Centre, Mordecai Ogada, Kerry Outram, Nick Georgiadis, Heather Wallington and Bard College. Roy Snelling provided insect identification training. Field and laboratory assistance were provided by Frederick Erii, John Lochukuya, Lynne Gadd, Abdi Kadir Ali Hassan, James Ponoto, Kadir Age, Francis Ewaton and University Research Expeditions Program volunteers. The manuscript was improved by comments from Scott Robinson and two anonymous reviewers.
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Ogada, D.L., Gadd, M.E., Ostfeld, R.S. et al. Impacts of large herbivorous mammals on bird diversity and abundance in an African savanna. Oecologia 156, 387–397 (2008). https://doi.org/10.1007/s00442-008-0994-1
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DOI: https://doi.org/10.1007/s00442-008-0994-1