Breeding Ecology and Multi-scale Niche Differentiation in Three Sympatric Hornbill Species in Yingjiang, SW China

Abstract Because breeding life histories show pronounced spatial and interspecific variation, accurately characterizing life-history traits of endangered species across populations and describing ecological differentiation from closely related sympatric species are essential for developing scientifically grounded conservation strategies. During the breeding seasons (Feb–Aug) from 2023 to 2025, we investigated the breeding ecology of three sympatric hornbill species in Yingjiang, Yunnan, China: Great Hornbill (Buceros bicornis), Wreathed Hornbill (Rhyticeros undulatus), and Oriental Pied Hornbill (Anthracoceros albirostris). The Wreathed Hornbill had the longest breeding period (125 days), whereas the Oriental Pied Hornbill had the shortest (82 days). The Great Hornbill initiated breeding earliest, whereas the Oriental Pied Hornbill initiated breeding latest, indicating clear interspecific differentiation in breeding timing. The Great Hornbill also used nest trees with larger diameters than the Oriental Pied Hornbill, whereas most other nest-site variables overlapped broadly among species. All three species relied heavily on Moraceae fruits, but the Oriental Pied Hornbill occupied a more distinct position in diet space and showed the broadest dietary niche breadth. Integrated analyses revealed clear separation among the three species in multivariate space. This study provides the first detailed account of breeding ecology in three hornbill species in China, describes multidimensional differences in breeding-season resource use, and offers a descriptive baseline for conservation planning and future tests of interspecific interactions.