The influence of temperature on parental investiment in Common Fiscal and consequences for nestling growth

Abstract

Global climate models project a 1.5-4oC increase in the Earth’s temperature by 2100. Africa, especially southern Africa, is expected to experience not only an increase in average temperatures but also an increase in the frequency and duration of extreme temperature events. Increasing temperatures will result in increased vulnerability to heat and drought stress to biodiversity. A recent paper by Cunningham et al. (2013) showed that temperature has a negative effect on daily mass gain in the nestlings of Common Fiscal (Lanius collaris) breeding in the southern Kalahari. This effect may be driven by parents modifying their provisioning rates at high temperature, but the mechanisms underpinning the relationship are not known. I investigate the influence of temperature on parental investment in Common Fiscal and the consequences of high temperatures for nestling growth using data from videos that were filmed in the Kalahari, Northern Cape, South Africa. Daily mass gain by nestlings increased with increasing provisioning rate and decreased in relation to the proportion of time chicks spent panting. Prey provisioning decreased with temperature in larger broods, however, there was no evidence to suggest that parents trade off provisioning and nest attendance. This might mean that prey availability is reduced at high temperatures, or that parents prioritise their own thermoregulation over provisioning.