Effects of high temperatures on nestling growth and physiology in the Southern Ground Hornbill Bucorvus leadbeateri
Carrie Hickman (M.Sc. student)
Supervisors: Dr. Susan Cunningham, Dr. Rita Covas

Daily maximum temperatures have increased in southern Africa over the last three decades, and the increase in temperature and frequency of extreme whether events is predicted to continue over the coming decades. Recent work in birds has shown that during hot weather individuals decrease their foraging activity and efficiency, which can lead to lower provisioning rates of dependent young, resulting in reduced growth. In addition, developing young may be directly affected by hot temperatures, as their need for evaporative water loss increases, and some physiological functions may become compromised. Under these extreme conditions, the location and characteristics of nests may have a strong influence on the environment experienced by the developing young and parents are expected to select cooler sites. This, however, may not be possible for cavity nesting species, which are limited by the natural cavities available or, in some cases, by artificial nests structures provided. 

The Southern Ground Hornbill (SGH) is a large cooperatively breeding bird that became endangered in South Africa as a result of habitat loss. These birds are cavity-nesters and the lack of suitable nesting sites has been a key factor in their decline. Fortunately, the birds readily occupy artificial nest boxes. Here, our specific objectives will be: 1) to investigate whether high ambient and nest temperatures lead to detrimental sub-lethal effect in developing SGH nestlings – measured as nestling growth, fledging size and condition, and telomere length (telomere length has been shown to be directly influenced by physiological stress and to correlate strongly with survival probability); 2) to use piecewise modelling (a type of path analyses) in order to investigate whether these negative effects arise from a decrease in the frequency or quality of nest provisioning by adults or from direct effects of temperature on the developing nestling.

 It is expected that a better understanding of whether SGH nestlings are suffering from high temperatures and how these effects arise, will allow us to propose measures to decrease possible detrimental effects of temperature in this species.

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