Edge Effects On Avian Distribution And Reproductive Success In Fragmented Secondary-forest

During the bird breeding seasons in 2005 and 2006, we investigated 11 patch size using GPS and observed bird species and quantity in fragmented forest in order to analyze edge effects on bird distribution in Zuojia Natural Protection Area in Jilin province. In addition, we put up nest-boxes in 5 secondary deciduous forest to measure reproductive parameter of great tit in order to analyze edge effects on bird reproductive success. The patch size changes between 10.9 and 51.2 hm2, with average size 24.8 hm2; The total area of patch with 226 nest-boxes is 134.5 hm2.The result showed that the shape index and isolation index of patch had a great change, with forest fragmented index 0.399. The edge effects on bird distribution mainly account for following sides:Different bird species had different reflection for patch size, and significant differences for some species in different patch. There are significant differences (P<0.01) between these two years for Bird population size. The regression model obtained: bird species had power function relationship with patch size, as patch size enhances, the bird species increase as well. Our results support classical island biogeography theory. There are negative correlation between bird density and patch size, but without significant difference. Therefore, patch size all had effects on bird diversity and density, with bigger size patch having more bird species and less size patch having biggish bird density.There are significant differences between Bird distribution and patch shape(P=0.032), and differences for bird density in different patch, but without significant differences(P=0.594). The regression model obtained: bird diversity and density had quadratic equation relationship with island shape. Bird species increase as abnormity enhances. There are negative correlation between bird density and patch shape index. Bigger abnormity patch had more bird species, while less abnormity patch had biggish bird density.The patch isolation had great effect on bird diversity and density, but without significant differences(P>0.05). The regression model obtained: bird diversity and density had quadratic equation relationship with patch isolation. Bird diversity and density differs with Patch isolation's movement. The patch isolation between 5 and 10 contained less bird species and density, while the rest patch had more bird species and density.By investigating bird species and amount in different distance grade, we obtained that bird mainly concentrated in 0~50 m and 50~100 m, with bigger species percent (54.65%) and amount percent (63.02%) in the two grade than the farness distance grade. Bird species moved to stabilization at inside distances, but amount going less and less. The nonparametric statistics showed that edge effects indeed existed, because there are significant differences between bird diversity & density and distance grade(P=0.00).Otherwise, 0~150 m differed from other distance grade with significant differences for bird diversity as well as bird density, especially from long-distance.By analyzing reproductive success of Great Tit, we obtained that the clutch size in different distance all reached 10, and the best existed in 50~100m.Egg weight had no rule and moved to stabilization. Egg volume had positive correlation with distance. The hatch rate and flying rate reached the biggest in 50~100 m, then appeared decline trend. The nonparametric statistics showed that the reproductive parameter had no significant differences in different distance (P>0.05), and edge effects had no significant effect on reproductive parameter of Great Tit.Anyway, edge effects played a great important role in bird breeding from patch size, patch shape, patch isolation, patch edge width et al. The analysis results showed that edge effect had little effects on secondary-cavity birds with great nest security, eg. Great Tit. The factors to affect bird reproduction are mainly competition and nest predation. From the bird distribution, we considered the best edge width as 150 m in secondary deciduous forest, with the most bird and significant differences than inside distance.