A Study of Resource Seletion by Black Kites (Milvus migrans) in the Urban Landscape of National Capital Region India

Abstract

Black Kites are the scavenger and predator raptors of the old world. In India they are synanthropic and perform the ecological role of city scavengers. Abundance and distribution of these birds suffers change due to rapid infrastructural changes in the developing cities which likely limit or change spatial layout of the available habitat and food. Many cities in the old world (London, Cape Verde, Istanbul) have experienced decline in the population of Milvus kites owing to rapid urbanization. Indian sub-continent almost lost its main scavenger, white backed vultures, in the last century. After this loss; existence of black kites, the most abundant raptor of the old world proves very vital. On these lines I carried carry out this dissertation from December 2012 to April 2013. This study focused on a) estimating the abundance of Black Kites on the Ghazipur dump site and the abundance of nesting pairs in National Capital Region (NCR), b) evaluating factors influencing nesting habitat selection combined with a broad understanding of its foraging habits and c) estimating nest survivorship in the urban landscape. I studied these parameters at selective study sites in NCR by intensive counts of birds at Ghazipur and breeding pairs at nest sites across eight study sites. Nests were searched intensively at each site while I tried to develop and test a new method to count the kites on the Ghazipur dump. Data from 116 nests and nest sites covariates were used to model nest survivorship under Known Fate scheme in Programme MARK. For my first objective, I estimated the current abundance of nesting pairs of Black Kites at 7 study sites. It ranged from 4 pairs / km2 in Sagarpur to 67 pairs / km2 in North Campus area. Nesting kites were selective while choosing a nest site, as evident by significant partial correlation between nest density, food index and green cover. The sites at the best trade-off between green cover and food availability had the highest nest densities. While developing a new methodology, I estimated around 2400 kites on the Ghazipur dump. Through behavioural observations and broad examination of regurgitated pellets, I could confirm scavenging as well as predacious nature of Black Kites. The overall probability of a nest to produce a viable fledgling was 0.45. The nest survivorship was stage specific and varied with pre-laying, incubation or nestling stage. The lower survival probability (0.60) at pre-laying stage is likely because of surplus nest formation at sites with good foraging opportunities. Understanding the importance of kites in urban ecology, studies using individually marked birds will reveal vital details of their behavioural and physiological adaptations. If future long term studies are conclusive enough, may establish Black Kites as an umbrella species of urban ecology.