Volume 3 • 2015 10.1093/conphys/cov048 Research article The role of thermal physiology in recent declines of birds in a biodiversity hotspot Downloaded from https://academic.oup.com/conphys/article-abstract/3/1/cov048/2571269 by guest on 06 November 2018 Robyn Milne1,†, Susan J. Cunningham1,†, Alan T. K. Lee1,2 and Ben Smit3,* 1Percy FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa 2Birds and Environmental Change Programme, Climate Change and Adaptation Division, South African National Biodiversity Institute, Claremont 7735, South Africa 3Centre for African Conservation Ecology, Department of Zoology, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa *Corresponding author: Centre for African Conservation Ecology, Department of Zoology, Nelson Mandela Metropolitan University, Port Elizabeth 6031, South Africa. Tel: +27 41 504 2421. Email:
[email protected] We investigated whether observed avian range contractions and population declines in the Fynbos biome of South Africa were mechanistically linked to recent climate warming. We aimed to determine whether there were correlations between preferred temperature envelope, or changes in temperature within species’ ranges, and recent changes in range and popula- tion size, for 12 Fynbos-resident bird species, including six that are endemic to the biome. We then measured the physiological responses of each species at air temperatures ranging from 24 to 42°C to determine whether physiological thermal thresholds could provide a mechanistic explanation for observed population trends. Our data show that Fynbos-endemic species occu- pying the coolest regions experienced the greatest recent reductions in range and population size (>30% range reduction between 1991 and the present).