Temporal changes in prey composition and biomass delivery to African Crowned Eagle nestlings in urban areas of KwaZulu-Natal, South Africa

Globally urban areas are expanding rapidly and this usually has negative effects on biodiversity. Despite this, some species manage to persist in urban areas, as is the case with African Crowned Eagles <i>Stephanoaetus coronatus</i> in KwaZulu-Natal, South Africa. As relatively little is known about African Crowned Eagle nestling diet, especially about how it changes with nestling age, we investigated this with nest camera-traps. We analysed temporal changes in prey composition and biomass delivery during the nestling stage. We also recorded which adults provisioned and attended the nest. The main prey fed to nestlings were Rock Hyrax <i>Procavia capensis</i> and Hadeda Ibis <i>Bostrychia hagedash</i>. Adult males did most of the food provisioning, especially at the start of the nestling period. We found a decrease in total prey number and biomass with nestling age. This may be caused by changing requirements of nestlings. Furthermore, delivering fewer prey at later nestling stages may be a facilitating mechanism to enhance fledging of the nestling. Although the total number of prey brought to the nest decreased, we found an increase in numbers of Vervet Monkey <i>Chlorocebus pygerythrus</i> in the diet with nestling age. This indicated an increase in larger prey being delivered to the nests as the nestling aged. We suggest that this could be caused by increased participation in hunting by the larger female as her nest attendance time decreased as the nestling aged. We conclude with emphasising the importance of protecting the Durban Metropolitan Open Space System (D’MOSS) zones for the persistence of this Near Threatened raptor species, and populations of its prey in urban areas for its breeding success.

全球城市区域正快速扩张，通常会对生物多样性造成负面影响。尽管如此，仍有部分物种能够在城市生境中存续，南非夸祖鲁-纳塔尔省的非洲冕雕（*Stephanoaetus coronatus*）即为典型案例。鉴于目前针对非洲冕雕雏鸟食性的研究相对匮乏，尤其是食性随雏鸟日龄的变化规律，我们借助巢式相机陷阱开展了相关调查。我们分析了雏鸟育雏期内猎物组成与生物量输送的时间动态特征，同时记录了参与食物投喂与巢区值守的成鸟个体信息。投喂给雏鸟的核心猎物为岩蹄兔（*Procavia capensis*）与哈达朱鹭（*Bostrychia hagedash*）。雄性成鸟承担了绝大多数的食物投喂工作，尤其在育雏初期阶段表现突出。研究发现，随着雏鸟日龄增长，巢穴接收的猎物总数量与总生物量均呈下降趋势，这可能与雏鸟的需求变化有关。此外，育雏后期减少猎物投喂量或许是一种辅助策略，以提升雏鸟的出巢成功率。尽管送往巢穴的猎物总数量有所减少，但我们发现雏鸟食谱中黑长尾猴（*Chlorocebus pygerythrus*）的占比随雏鸟日龄增长而显著上升，这意味着随着雏鸟发育，投喂的大型猎物比例有所提升。我们推测，这一现象可能源于随着雏鸟日龄增加，雌性成鸟的巢区值守时间缩短，从而更多地参与到狩猎活动中。我们在研究结尾强调，保护德班都市开放空间系统（Durban Metropolitan Open Space System，简称D’MOSS）区域，对于这一近危猛禽物种的存续至关重要；同时保护其在城市区域的猎物种群，亦是保障该物种繁殖成功的关键环节。