Abstract

More and more continuous forests become fragmented because of natural events and human disturbance. This change will affect the distribution patterns and behavior characteristics of animals living in forests. Using point count methods, we investigated bird species diversity and individual density in 18 forest fragments (area: 4.3 to 76.9 hm2) in Zuojia Nature Reserve, Jilin Province during the spring and summer of 2000 and 2001. The main objectives of this research were to assess whether there exist area effects affecting bird species diversity and individual density in a fragmented forest. There was no significant difference of indices of bird diversity between the two years. However, the individual density of birds differed signifi-cantly in the two years. Our results also indicated that there were significant differences in bird diversity among forest patches, with the number of bird species ranging from 12 to 43. Although several large forest patches contained relatively fewer bird species, the bird species tended to increase with size of forest patch. Different bird species respond to forest patch size differently. White-checked starling (Sturnus cineraceus), brown shrike (Lanius cristatus) and black-faced bunting (Embriza spodocephala) preferred small patches, whereas forest wagtail (Dendronanthus indicus), olive-backed pipit (Anthus hodgsoni) and grey-backed thrush (Turdus hortulorum) rarely occurred in small patches. Basically, the relationship between area size and species number was in accordance with the classical theory of island biogeography, but the Z and C values were very different from those predicted. We found a threshold phenomenon in the relationship between patch area and number of bird species such that the number of bird species did not change significantly when the patch size was greater than 30 hm2. Thus, it is not suitable to use the classical theory of island biogeog-raphy directly to predict species diversity or for designing nature reserves for a fragmented forest landscapes.