Supporting data for "Dietary niche partitioning of birds in Hong Kong"

Understanding the dietary niche of species is an important aspect of the study of ecology. Ecologists have long been trying to understand the uniqueness of a species in terms of their requirements for life and interactions with other organisms. The distinctiveness of ecological niches allows the coexistence of various species and gives rise to biodiversity. In this thesis, I aimed to investigate the ecological niche of birds in Hong Kong, with a focus on their dietary requirements and their functional role as plant seed dispersers, using a molecular approach and seed germination experiments. In the first data chapter, I identified the dietary compositions of migratory passerines in farmland. Six species of bunting (Genus: Emberiza) were captured from open-field farmland in Hong Kong in winter 2019 and faecal samples were collected. I performed DNA metabarcoding on DNA extracted from faecal samples and analyzed differences in their diets. I found that Yellow-breasted bunting E. aureola occupied a distinct niche of consuming more paddy rice than other Emberiza species in the same habitat. In addition, many wild grasses, such as Echinochloa and Digitaria, were found to be major food sources for migrating Emberiza species. Efforts were made to determine the potential contributing factors for the variations in dietary compositions within species. However, this study could not conclude any significant correlations. Knowledge of the dietary niche of Emberiza species will be useful to inform future conservation programmes. In the second data chapter, I examined the dietary niche and seed dispersal service of frugivorous avian species in disturbed landscapes. I collected faecal samples from five species of common birds resident in the secondary forest of Hong Kong, including the introduced Huet’s Fulvetta Alcippe hueti, Silver-eared Mesia Leiothrix argentauris, Red-billed Leiothrix Leiothrix lutea, Rufous-capped Babbler Stachyridopsis ruficeps, and native Swinhoe's White-eyeZosterops simplex. I identified the temporal variations and compositions of their diets and evaluated their roles as seed dispersers by DNA metabarcoding, seed counting, and seed germination experiments. Their diets mainly comprised a high variety of plants. The observed lack of specificity in plant-bird interactions suggests that both plant and avian communities are largely generalist. No clear patterns of dietary partitioning or seed dispersal service segregation were found between species. Furthermore, seed germination experiments revealed these birds were effective seed dispersal agents for many local shrubs, trees and climber species, despite ingested seeds generally taking a longer time to germinate compared to control seeds directly extracted from intact fruits. Temporal variations were detected in the diets of woodland birds, which were closely associated with the fruiting phenologies of plants. Overall, as frugivory and seed dispersal are important ecological processes, knowledge of plant-bird dynamics will shed light on the restoration of disturbed landscapes, such as secondary forests, and natural succession.