Abstract:
Southern ground-hornbills Bucorvus leadbeateri inhabit savanna and bushveld regions of
South Africa. They nest in the austral summer, which coincides with the wet season and
hottest daytime temperatures in the region. They are secondary cavity nesters and typically
nest in large cavities in trees, cliffs and earth banks, but readily use artificial nest boxes.
Southern ground-hornbills are listed as Endangered in South Africa, with reintroductions
into suitable areas highlighted as a viable conservation intervention for the species. Nest
microclimate, and the possible implications this may have for the breeding biology of
southern ground-hornbills, have never been investigated. We used temperature dataloggers
to record nest cavity temperature and ambient temperature for one artificial and 11 natural
southern ground-hornbill tree cavity nests combined, spanning two breeding seasons. Mean
hourly nest temperature, as well as mean minimum and mean maximum nest temperature,
differed significantly between southern ground-hornbill nests in both breeding seasons.
Mean nest temperature also differed significantly from mean ambient temperature for both
seasons. Natural nest cavities provided a buffer against the ambient temperature
fluctuations. The artificial nest provided little insulation against temperature extremes,
being warmer and cooler than the maximum and minimum local ambient temperatures,
respectively. Nest cavity temperature was not found to have an influence on the breeding
success of the southern ground-hornbill groups investigated in this study. These results have
potentially important implications for southern ground-hornbill conservation and artificial nest design, as they suggest that the birds can tolerate greater nest cavity temperature
extremes than previously thought.
