vultures along with some 50 other species of birds have migrated from Delhi in the last few years as their traditional habitats have made way for unplanned urban development, says Rupin Dang, a naturalist. Bird counts and other census data show that about 30 years ago, the capital was home to at least 400 species of birds but today the figure has come down to 350. "The Golden Oriole has just disappeared, since no one grows fruit trees anymore with dense canopies. Instead, it has migrated to private farms on the periphery of the city," says Dang. Bird counts conducted by the World Wildlife Fund and Kalpavriksh, a non-governmental organisation, show that the numbers of some species in the city vary from year to year. Orthinologists cite the example of the Striated Grass Warbler that were spotted recently after a period of 80 years during which time, some experts believed it had become extinct.