Combrink L, Combrink H J, Botha A J, Downs C T
School of Life Sciences, University of KwaZulu-Natal, P/Bag X01, Scottsville, Pietermaritzburg 3209, South Africa; The Endangered Wildlife Trust, P/Bag X11, Modderfontein, Johannesburg 1645, South Africa.
Department of Veterinary Tropical Diseases, University of Pretoria, P/Bag X04, Onderstepoort, Pretoria 0110, South Africa.
J Therm Biol. 2017 May;66:21-26. doi: 10.1016/j.jtherbio.2017.03.003. Epub 2017 Mar 12.
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.
南非地犀鸟（Bucorvus leadbeateri）栖息于南非的热带稀树草原和灌木草原地区。它们在南半球的夏季筑巢，而此时正值该地区的雨季和白天最热的时段。它们是次级洞巢鸟，通常在树木、悬崖和土堤的大洞穴中筑巢，但也很乐意使用人工巢箱。南非地犀鸟被列为濒危物种，将其重新引入适宜区域被视为对该物种可行的保护措施。巢的微气候及其对南非地犀鸟繁殖生物学可能产生的影响从未得到过研究。我们使用温度数据记录器，在两个繁殖季节中，对1个人工巢和11个天然的南非地犀鸟树洞巢的巢洞温度和环境温度进行了记录。在两个繁殖季节中，南非地犀鸟巢的平均每小时巢温、平均最低巢温和平均最高巢温均存在显著差异。两个季节的平均巢温与平均环境温度也存在显著差异。天然巢洞可缓冲环境温度的波动。人工巢对极端温度几乎没有隔热作用，分别比当地最高和最低环境温度更暖和或更凉爽。在本研究中，未发现巢洞温度对南非地犀鸟种群的繁殖成功率有影响。这些结果对南非地犀鸟的保护和人工巢设计可能具有重要意义，因为它们表明，这种鸟类能够耐受比之前认为的更大的巢洞温度极端变化。
