Read the given passage and answer the questions that follow.
The usual perception of a wetland is a sprawling lake far away from a city, distant from humans, entirely pristine and therefore, lush with biodiversity. However, our research presents interesting new findings about these entities. Wetlands are in fact embedded in our towns and cities. It is often believed that such urban water bodies aren’t ecologically useful. But these water bodies play a crucial role in supporting bird life — and the ecosystem services this brings. Our research explored ponds across Delhi which is quite unique in terms of retaining many urban forests, a protected floodplain and patches of the Aravalli hills. These diverse habitats — and the location of Delhi in the middle of a major migratory pathway of birds — have led to over 470 bird species being recorded in the city, the second-longest such list for any capital globally.
A major reason for this avian abundance is that the Delhi Development Authority (DDA) disallows the destruction of water bodies over a hectare in size. This has enabled 570 ponds to survive — the histories of these ponds are as varied as their appearance, from being village ponds to temple tanks, rainwater harvesting structures, water bodies made in parks, etc. Delhi’s ponds aren’t managed collectively — each is in the hands of municipalities, welfare associations or other institutions. Consequently, every pond has its own characteristics. Some are heavily managed, others are entirely ignored, some are accessible, others are hard to approach. The water quality, garbage levels and foliage also vary. Importantly, this variety allows multiple birds to use these ponds. We found at least 177 species at the 39 water bodies — ponds comprise less than 0.5% of the area of Delhi but provide a home to over 40% of the city’s bird species. These included species of global conservation concern like the common pochard, the ferruginous pochard, the river lapwing, the black-headed ibis and the painted stork. Also, ponds with less management interventions had greater diversity of habitats birds could use — as these interventions grew, the number of bird species declined. We found 46% birds were wetland specialists while the rest used the trees and shrubs on the edges of ponds.
The main theme of the passage is: