Flush Distance: Bird Tolerance to Human Intrusion in Hangzhou

Flush distance, how close one can get to a bird before it flushes, reflects the adaptation of birds to human intrusion.A larger flush distance indicates a lower adaptation to human intrusion.To examine the patterns of the adaptation of birds to human intrusion and its influencing factors,9 dominant and widely-distributed species were selected among 42 species surveyed in Hangzhou,China from September 2002 to January 2003.Based on the differences in vegetation type,building index and disturbance degree,habitats were divided into 5 categories:building areas,urban woodlots,western mountains,ponds and farmlands.Four variables reflecting biological traits of birds (body size,activity height,migratory status,conspicuousness) and one habitat variable (visibility of observation point) were selected to examine their influence on flush distance.We found that:1)The degrees of human intrusions in 5 habitats were significantly different.2)There were significant differences in the flush distance of 9 species among different habitats.Generally,the flush distance was negatively associated with human intrusion.3)The analysis of bivariate correlation showed that flush distance was positively associated with body size and the visibility of observation point,but it was negatively associated with activity height.However,there was no significant association between the flush distance and the conspicuousness of birds.Our results indicated that most species had adapted to human intrusions to some extent,and that the birds with larger body,or those occurred in the habitats with higher visibility or closer to the ground had relatively lower adaptation to human intrusions.