Supporting data for "Dietary niches of birds in Hong Kong"

Understanding the dietary niche of birds has significant implications for the trophic interactions in ecosystems. Hong Kong has remarkably high biodiversity in both habitats and avian species. However, the dietary niches of many birds in Hong Kong remain understudied.This thesis investigated the dietary niche of birds in Hong Kong, with a focus on niche partitioning and their functional role as plant seed dispersers.<br>This thesis first analyzed the stopover diets of the critically endangered Yellow-breasted bunting (<i>Emberiza aureola</i>) and five other sympatric bunting species, namely Little bunting (<i>Emberiza pusilla</i>), Chestnut-eared bunting (<i>Emberiza fucata</i>), Yellow-browed bunting (<i>Emberiza chrysophrys</i>), Black-faced bunting (<i>Emberiza spodocephala</i>) and Rustic bunting (<i>Emberiza</i><i> </i>rustica) in Hong Kong. A total of 109 faecal samples were analyzed using DNA metabarcoding with multiple markers (18S, ITS2 and COI) to ensure a comprehensive coverage of dietary diversity. It was revealed that all bunting species primarily consumed Poaceae, with the Yellow-breasted bunting occupying a distinct niche by consuming a high proportion of cultivated <i>Oryza</i><i> </i>(rice) compared to other sympatric bunting species. Conversely, other bunting species shared a highly similar diet. Furthermore, wild grasses, such as <i>Echinochloa</i> and <i>Digitaria</i>, were identified as major food sources for migrating buntings. Individual variations in dietary composition were observed between conspecific Yellow-breasted buntings. Morphological measurements such as wing length, tail length, weight and the amount of fat stored were found to have limited influence on these variations. Knowledge of the dietary requirements of buntings will be useful to inform future conservation programmes.<br>The second study focused on identifying the dietary compositions of five common resident bird species in secondary forest in Hong Kong, including the introduced Huet’s Fulvetta<i> </i><i>Alcippe hueti</i>, Silver-eared Mesia<i> </i><i>Leiothrix argentauris,</i> Red-billed Leiothrix<i> </i><i>Leiothrix lutea</i>, Rufous-capped Babbler<i> </i><i>Stachyridopsis ruficeps</i>, and native Swinhoe's White-eye<i> </i><i>Zosterops simplex</i>. A total of 107 faecal samples were analyzed using DNA metabarcoding with three markers (18S, ITS2 and <i>trnL</i>) while an additional 48 samples were examined for seed germination experiments. The results revealed that the diets of these birds mainly consisted of a diverse range of plants and a limited amount of invertebrates. Their diets and seed dispersal services were highly overlapping. However, seasonal variations were observed in the diets of forest birds, which were closely associated with the fruiting phenologies of plants. Additionally, it was found that these birds were seed dispersers for many native shrubs that exhibit avian dispersal syndromes. Furthermore, ingested seeds generally took a longer time to germinate compared to control seeds extracted directly from intact fruits. Overall, seed dispersal through birds is an important ecological process, knowledge of plant-bird trophic interactions and seed dispersal patterns will shed light on the restoration of secondary forests, and natural succession.This thesis successfully demonstrated the use of DNA metabarcoding to provide fundamental information on the dietary niches of migratory buntings and resident forest birds, as well as their associated ecological functions in Hong Kong. The findings of this study will be valuable for future ecological research and conservation efforts.

解析鸟类的食物生态位，对生态系统中的营养级交互具有重要意义。香港地区的生境与鸟类类群均具备极高的生物多样性，但当地多数鸟类的食物生态位仍未得到充分研究。本研究针对香港地区鸟类的食物生态位展开探究，重点关注生态位分化以及它们作为植物种子传播者的生态功能。
本研究首先分析了极危物种黄胸鹀（*Emberiza aureola*）及另外5种同域分布鹀类在香港的停歇期食性，这5种鹀类分别为小鹀（*Emberiza pusilla*）、栗耳鹀（*Emberiza fucata*）、黄眉鹀（*Emberiza chrysophrys*）、灰头鹀（*Emberiza spodocephala*）和田鹀（*Emberiza rustica*）。本研究共采集109份粪便样本，采用包含18S、ITS2及COI在内的多标记物DNA宏条形码（DNA metabarcoding）技术进行分析，以全面覆盖食性多样性。研究发现，所有鹀类均以禾本科植物为主要取食对象；相较其他同域鹀类，黄胸鹀因取食高比例的栽培稻属（*Oryza*）植物（即水稻）而占据独特的生态位。反之，其余鹀类的食性高度相似。此外，稗属（*Echinochloa*）和马唐属（*Digitaria*）等野生禾草被确定为迁徙鹀类的主要食物来源。同种黄胸鹀个体间的食性组成存在差异，而翅长、尾长、体重及体脂储存量等形态指标对这类差异的影响有限。掌握鹀类的食性需求，可为后续的保护计划提供科学依据。
第二项研究聚焦于香港次生林内5种常见留鸟的食性组成，包括引入种褐胁雀鹛（*Alcippe hueti*）、银耳相思鸟（*Leiothrix argentauris*）、红嘴相思鸟（*Leiothrix lutea*）、红头穗鹛（*Stachyridopsis ruficeps*）以及本土种暗绿绣眼鸟（*Zosterops simplex*）。本研究共采集107份粪便样本，采用包含18S、ITS2及*trnL*在内的3种标记物的DNA宏条形码技术进行分析；此外还额外选取48份样本开展种子萌发实验。结果显示，这些鸟类的食物主要由多种植物以及少量无脊椎动物构成。它们的食性与种子传播服务存在高度重叠，但森林鸟类的食性存在季节差异，这与植物的结实物候紧密相关。此外，研究发现这些鸟类可为多种具备鸟类传播综合征的本土灌木传播种子。与直接从完整果实中取出的对照种子相比，经鸟类取食的种子通常需要更长的萌发时间。总体而言，鸟类介导的种子传播是一项重要的生态过程；掌握植物-鸟类营养级交互与种子传播模式，可为次生林恢复与自然演替研究提供参考。
本研究成功验证了DNA宏条形码技术可用于获取香港地区迁徙鹀类与林栖留鸟的食物生态位基础信息，以及它们对应的生态功能。本研究的发现可为后续生态研究与保护工作提供重要参考。