There has been a gradual decline in the natural vegetation around Madras. The reduction and fragmentation of the mainly tropical, dry, evergreen forest, also called scrub jungle, has led to the extinction of bird species, particularly those that are habitat-specific.

Studies showed more migratory birds were found where new trees and shrubs were planted than in scrub sites (Blackbuck, Vol 8 No 1). There were also more transients in natural scrub sites, indicating these patches were feeding grounds for bird from adjacent areas. The proportion of habitat-specific species was also higher in natural scrub sites than in modified areas. The studies say as a natural scrub area degrades, their species composition gets altered, with the main victims being habitat-specific birds.