| Summary: | 碩士 === 國立臺灣大學 === 生態學與演化生物學研究所 === 106 === Urbanization results in loss of natural habitats and biodiversity. Bird assemblages are dominant by few species and share more similarity in highly urbanized regions, so called “biotic homogenization”, which raises concern of urban biodiversity. However, most of studies focused on spatial patterns. How assemblages changed over time is relatively unexplored. Hence, this study used monitoring data of 16 Taipei parks from 2003 to 2017 to investigate temporal changes of bird assemblages. We used similarity indices to examine the effects of exotic species on biotic homogenization. Then, we used five traits (residence status, diet, foraging site, nesting site and habitat) and three indices (richness, abundance, relative abundance) to determine if there were different temporal trends in guilds.
The results demonstrated an upward trend in both overall species richness and total abundance. After excluding exotic species, similarity indices decreased through time, which implied that they to some degree drove the homogenization of assemblages. Guilds exhibited different trends. Exotic species, omnivores, insecti/frugi/granivores, aquatic/granivores, aquatic foragers and forest generalists significantly increased in all indices. Most of guilds had positive trends in richness and abundance, but rates of increase were divergent. Omnivores increased faster than other diet guilds, which may result from their ability to utilize a variety of food types, including human-provided food. Increase of water-associated species, such as aquatic/granivores and aquatic foragers, reflected a good aquatic environment in Taipei city. Forest generalists indicated positive trends in all indices; however, forest specialists showed a faster increase in richness and abundance. Though forest specialists used to be viewed as urban avoiders, this study deduced that supplements of suitable habitats can support their population in urban areas. The same situation was also found in ground nesters; however, there is still a lack of directly environmental evidence. In addition, exotic species and cavity/building nesters shared similar change patterns; thus, the ability to nest in man-made structures may be important for them to adapt well in urban environments. With the long-term monitoring data, the study provided the temporal perspective of bird assemblages, which can help to reach a more comprehensive and efficient actions of diversity conservation.
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