The impact of weather conditions on the competition and breeding success of three sympatric hornbill species in a semi-arid region

Recent studies have highlighted the vulnerability of hornbills breeding in hot, arid environments, raising concern about the species’ persistence with climate change. Hornbills are, however, a widespread avian family found in various climates in Africa and Asia. In this study, we investigated the factors impacting the breeding phenology of three sympatric African hornbill species in a semi-arid environment. We found that rainfall was associated with breeding initiation and breeding success in all three species (African grey hornbill Lophoceros nasutus, Southern yellow-billed hornbill Tockus leucomelas, and Southern red-billed hornbill Tockus rufirostris). Breeding success and chick body mass change of African grey hornbills and Southern yellow-billed hornbills, but not Southern red-billed hornbills, were negatively impacted by high air temperatures during the breeding season. This study shows that Southern red-billed hornbills were more successful at producing offspring compared to African grey hornbills and Southern yellow-billed hornbills, which was likely due to their later breeding initiation compared to the other two species. Future changes in rainfall patterns may cause the African grey hornbills and Southern yellow-billed hornbills to delay breeding activities. Delayed breeding could result in a greater overlap of the nesting period of the three species, which would, in turn, increase the competition for food and suitable nesting sites. This study confirms that also in semi-arid areas, climate change has the potential to affect the breeding success of hornbills.