Abstract:

Aims: Avian dietary studies are fundamental not only for understanding life-history traits but also for elucidating ecological adaptation and reproductive success. The red-billed leiothrix (Leiothrix lutea), a national second-class key protected species in China and a common insectivorous bird in the forests of southern China, exhibits highly secretive nesting and provisioning behavior during the breeding season. Consequently, the diet composition and diversity of its nestlings remain difficult to characterize accurately and comprehensively using conventional observational methods. This study aimed to assess the nestling diet of this species by integrating miniature camera monitoring with fecal DNA metabarcoding, and to evaluate the complementarity and respective limitations of the two approaches. 

Methods: Fieldwork was conducted from April to September 2025 in the Daweishan Provincial Nature Reserve, Liuyang, Hunan Province. Miniature cameras were deployed at active nests to continuously record parental provisioning behavior in a non-intrusive manner, and valid feeding events with identifiable prey items were extracted from the footage. Meanwhile, fresh nestling fecal samples were collected and subjected to DNA metabarcoding targeting the mitochondrial cytochrome c oxidase subunit I (COI) gene. Dietary composition obtained from the two methods was compared using the Sørensen similarity index and the Shannon diversity index. 

Results: Video monitoring recorded 274 valid feeding events and identified 11 invertebrate orders, with Orthoptera (29.45%), Mantodea (21.36%) and Hemiptera (19.42%) ranking highest in feeding frequency. DNA metabarcoding detected 12 invertebrate orders, with Lepidoptera (51.32%) and Hemiptera (37.17%) dominating the sequence relative abundance. The Sørensen similarity index between the two methods at the order level was 0.609, indicating moderate overlap. The Shannon diversity derived from sequencing data (3.386) was markedly higher than that from video monitoring (1.61), demonstrating that either method alone has inherent detection blind spots. 

Conclusions: The nestling diet of the Red-billed Leiothrix consists of both large-bodied and small-bodied prey: the former provide the energetic foundation, while the latter ensure dietary diversity and the stability of food provisioning. Miniature cameras and fecal DNA metabarcoding are highly complementary in dietary analysis—video monitoring excels at recording feeding behavior and identifying large, morphologically distinct prey, whereas metabarcoding is more sensitive to small, soft-bodied or highly digested prey. Their combined application yields more comprehensive dietary information and provides a reliable technical framework for future avian dietary studies.

Key words: red-billed leiothrix, nestling diet, species diversity, miniature camera, DNA metabarcoding