Birds Adaptability To Urbanization

We studied the patterns of breeding, foraging and the tolerance to human disturbance of bird species across 3 urban gradients, by censusing birds at five sites in Hangzhou (excepting Xiaoshan district, Yuhang district etc.), China between March 2001 and January 2003. These sites represented 3 gradients of urban land use that ranged from relatively undisturbed to highly developed, and included western mountains, ponds, farmlands, urban woodlots and building areas. The main results were as follows:1. Fifty-eight species, belonging to 14 foraging guilds, were recorded in different habitats during the foraging survey period. There were 13 foraging guilds in western mountains and in ponds either, 7 foraging guilds in farmlands, 12 foraging guilds in urban woodlots, and 4 foraging guilds in building areas. Therefore, increasing level of urbanization on the whole reduced the total number of foraging guilds. Besides, some species changed foraging guilds accordingly with the change of foraging habitats.2. The analyses based on logistic regression showed there were significant relations between the occurrences of foraging guilds and habitat variables. Canopy cover, shrub cover and food abundance were main factors that influenced the occurrences of most foraging guilds. The occurrences of some foraging guilds were also related to mean tree height, tree species number and food diversity to some extents. For foraging guild 132, 342, 555 and 566, however, their occurrences were negatively associated with urbanization characteristic variables, such as distance to city center, human disturbance, building index and urbanization synthesis index etc. It meant that these guilds had poor adaptation to urbanization.3. At the species level, we selected 8 dominant species and ordinary species, which were Light-vented bulbul, Black-billed magpie, Eurasian tree sparrow, Eurasian blackbird, Great tit, White wagtail, Vinous-throated parrotbill and Spotted dove, to assess their adaptations to urbanization.To analyze the adaptation as to the food habits of birds conveniently, we divided all the food into 2 categories: (1) urban food, which included food distributed mainly in city, such as bread, rubbish scrap etc.; (2) natural food, which didn't contain any urban food atall and was distributed mainly in natural habitats.Based on curve estimation, the analyses indicated that the foraging frequencies on urban food of 8 species was positively associated with urbanization synthesis index. It implied that some species could use urban food successfully, and these species had adapted to urbanization in the way of foraging habits.4. One-way ANOVA showed that mean foraging heights differed significantly among habitats for most species (excepting White wagtail and Vinous-throated parrotbill). On the whole, the mean foraging height decreased with the increase of urbanization along 3 urbanization gradients. It meant that most species had adapted to the height changes of food resources caused by urbanization.5. Based on field observation, we found the variations of bird foraging behaviors in different habitats. Increasing level of urbanization reduced the ratios of canopy gleaning, barker drilling, baker foraging and water area gleaning, but it increased the proportion of ground gleaning along urbanization gradients. The changes of these foraging behaviors were adaptations of birds to the changes of food resources resulted from urbanization.6. Forty-five species were recorded in all habitats in breeding season, and 23 breeding species and their 956 nests were recorded, but not any nest of other 22 species was found. Among 23 breeding species, Light-vented bulbul, Black-billed magpie, Eurasian tree sparrow, Eurasian blackbird, White-rumped munia, Vinous-throated parrotbill and Spotted dove were abundant in nest number and their nests were widely distributed. Hence, at the species level, these species were chosen to examine their adaptations to urbanization.7. Twelve habitat variables, including mean tree height, can...