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Direct and indirect effects of high temperatures on fledging success in a cooperatively breeding bird.

dataset
posted on 12.05.2021, 14:32 by Amanda Bourne, Amanda Ridley, Claire Spottiswoode, Susan Cunningham

High temperatures and low rainfall consistently constrain reproduction in arid-zone bird species. Understanding the mechanisms underlying this pattern is critical for predicting how climate change will influence population persistence and to inform conservation and management. In this study, we analysed Southern Pied Babbler Turdoides nestling survival, daily growth rate and adult investment behaviour during the nestling period over three austral summer breeding seasons. High temperatures were associated with lower body mass, shorter tarsi, and reduced daily growth rates of nestlings. Piecewise structural equation modelling suggests that direct impacts of temperature have the strongest influence on nestling size and daily growth rates for 5-day-old and 11-day-old nestlings, followed by temperature-related adjustments to provisioning rates by adults to older nestlings. Rainfall and group size influenced the behaviour of provisioning adults but not nestling size, daily growth rates or survival to fledging. Adjustments to adult provisioning strategies did not compensate for direct negative effects of high air temperatures on nestling body mass, tarsus and wing length, or daily growth rates. Detailed mechanistic data like these allow us to model the pathways by which high temperature causes nest failure. In turn, this could allow us to design targeted conservation action to effectively mitigate climate effects.

Funding

DST-NRF Centre of Excellence at the FitzPatrick Institute of African Ornithology

University of Cape Town

Oppenheimer Memorial Trust (grant number 20747/01)

British Ornithologists’ Union

Australian Research Council (grant number FT110100188)

National Research Foundation of South Africa (grant number 99050)

History

Department/Unit

Biological Sciences