Effects of Urbanization on the Avian Nesting Guilds in Hangzhou

We investigated the avian nesting guilds in Hangzhou across an urban gradient from March 2007 to August 2007. This gradient includes different urbanization level habitats of urban areas, rural-urban continuum areas, farmland areas, forestland mixed areas, and forestland areas, in order to recognize the effects of urbanization on avian nesting guilds. There were 18 strip transects (3 km×100 m) in each type of habitats, totaling 90 transects. Ninety-six bird species and 9 nesting guilds were recorded. Based on the locations of the nest sites, these were classified as canopy nesters, shrubs nesters, canopy/ shrub nesters, natural cavity nesters, buildings nesters, natural cavity/ buildings nesters, ground nesters, water surface nesters and parasite nesters. The results showed that the urbanization could decrease both the numbers of the nesting guilds and the species in nesting guilds. We found that the urbanization had different impact patterns for different nesting guilds. For example, the number of canopy nesters, shrub nesters, ground nesters and natural cavity nesters declined with increased urbanization. Shrub nesters and ground nesters were particularly more sensitive to urbanization. For the natural cavity/build nesters, numbers were increased with urbanization. The affecting patterns of urbanization were different with different nesting guilds as they using different nest-sites. Additionally, we found that although all of variables of habitat measured in our survey, the vegetation coverage, areas of buildings, distance to the city center and human disturbance could influence the avian community structure of nesting guilds, each variable had a specific pattern of the effect on the nesting guilds separately.