1. a Percy FitzPatrick Institute of African Ornithology, University of Cape Town, Rondebosch 7700, South Africa
2. b Environmental Policy Research Unit, School of Economics, University of Cape Town, Rondebosch 7700, South Africa
3. c Anchor Environmental Consultants, Steenberg House, Steenberg Office Park, Silverwood Cl, Tokai, Cape Town 7945, South Africa