Avian Community Structure of Urban Parks in Hong Kong: Effects of Urbanization and Multi-scale Habitat Characteristics.

摘要

Urban development affects avian community structure dramatically, and it is considered a major cause of native species extinction. Hong Kong is a highly urbanized city, but has great conservation values for birds particularly migrants. There is a paucity of information on the effects of urbanization and multi-scale habitat characteristics on urban birds in Hong Kong.;Parks are hotspots of avian diversity in urban landscapes. Thirty parks, scattered throughout the territory, were selected as sampling sites from developed and new growth areas. Bird community structure was studied in the breeding and wintering seasons in 2010-2011. Regarding the effects of urbanization, bird communities in the new growth areas were more homogeneous and nested than those in the developed areas. Residents dominated urban parks in both development types. More granivores and open-habitat species, but fewer insectivores, insectivore-frugivores, and forest-specialist birds appeared in the developed areas than in the new growth areas. These differences were strongly associated with habitat evenness and largest patch index for woodland at 400-m scale and contagion index at 400- and 1000-m scales.;There were obvious seasonal differences in urban bird communities. Species composition, richness, and diversity were significantly different between the breeding and wintering seasons. Compared to breeding bird communities, more insectivores, insectivore-frugivores, and species feeding on plants, but less granivores and species feeding on the ground appeared in the wintering season.;The effects of park attributes, human disturbance, and vegetation structure on the seasonal differences were determined. Species richness and diversity were positively affected by park size in both seasons. Species richness was negatively affected by visitor rate in the wintering season. Total bird density increased with visitor rate, but only in the breeding season. In other words, park size and visitor rate were the major factors affecting bird communities in both seasons. Moreover, different species groups had different responses to habitat characteristics in different seasons. For examples, migrants, insectivores, and insectivore-frugivores were positively affected by park size, but negatively by visitor rate in the wintering season. However, omnivores in the breeding season increased with both park size and visitor rate.;The effects of habitat characteristics at five landscape scales on wintering bird communities were addressed. Total species richness was significantly affected by the availability of woodland and grassland at 200-m scale. For the six selected species, the incidence of Fork-tailed Sunbird (Aethopyga christinae) was affected by patch density, positively at 200-m scale but negatively at 400-m scale, and the incidences of the other five species (including Pallas's Leaf Warbler Phylloscopus proregulus, Common Blackbird Turdus merula, Grey-backed Thrush T. hortulorum, Asian Koel Eudynamys scolopaceus, and Eurasian Magpie Pica pica) were best predicted by the availability of greenspaces within 400 m. Consequently, factors at fine scales (within 400 m) should be more concerned while conserving birds in Hong Kong.;Finally, the cross-scale effects of habitat measurements at 400-m landscape and local scale on wintering bird communities were examined. The percentage of woodland and patch density at landscape scale, and tree density at local scale were mostly strongly correlated with species distribution. Most species groups and the incidences of individual species were better predicted by cross-scale approaches, and landscape characteristics increased the efficiency of local-only models. It is necessary to simultaneously consider the joint effects of landscape- and local-scale characteristics on birds in urban environments.;This research is the first to systematically study bird communities in urban parks of Hong Kong, and determine the factors influencing bird distribution patterns at multiple scales. The knowledge acquired would help land owners and park managers to conserve a more diverse ecosystem in Hong Kong.