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South temperate birds have higher apparent adult survival than tropical birds in Africa
Authors:Penn Lloyd  Fitsum Abadi  Res Altwegg  Thomas E Martin
Institution:1. Percy FitzPatrick Inst., DST/NRF Centre of Excellence, Univ. of Cape Town, , P/Bag X3, Rondebosch, 7701 South Africa;2. Biodiversity Assessment and Management Pty Ltd, , PO Box 1376, Cleveland, 4163 Australia;3. South African National Biodiversity Inst., , P/Bag X7, Claremont, 7735 South Africa;4. School of Statistics and Actuarial Science, Univ. of Witwatersrand, , Johannesburg, P/Bag X3, Wits, 2050 South Africa;5. African Climate and Development Initiative, Univ. of Cape Town, , South Africa;6. Centre for Statistics in Ecology, Environment and Conservation, Dept of Statistical Sciences, Univ. of Cape Town, , Rondebosch, 7701 South Africa;7. U. S. Geological Survey Montana Cooperative Wildlife Research Unit, Univ. of Montana, , Missoula, MT 59812 USA
Abstract:Life history theory predicts an inverse relationship between annual adult survival and fecundity. Globally, clutch size shows a latitudinal gradient among birds, with south temperate species laying smaller clutches than north temperate species, but larger clutches than tropical species. Tropical birds often have higher adult survival than north temperate birds associated with their smaller clutches. However, the prediction that tropical birds should also have higher adult survival than south temperate birds because of smaller clutch sizes remains largely untested. We measured clutch size and apparent annual breeding adult survival for 17 south temperate African species to test two main predictions. First, we found strong support for a predicted inverse relationship between adult survival and clutch size among the south temperate species, consistent with life‐history theory. Second, we compared our clutch size and survival estimates with published estimates for congeneric tropical African species to test the prediction of larger clutch size and lower adult survival among south temperate than related tropical species. We found that south‐temperate species laid larger clutches, as predicted, but had higher, rather than lower, apparent adult survival than related tropical species. The latter result may be an artefact of different approaches to measuring survival, but the results suggest that adult survival is generally high in the south temperate region and raises questions about the importance of the cost of reproduction to adult survival.
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