Black kites in Delhi actively choose to live near humans, even accepting food that they offer. But the birds perceive people near their nests as potential predators, suggesting that they can react to people based on the context, shows a recent study published in the journal PLOS ONE .
In the country’s capital, black kites – birds of prey that are at home in concrete jungles – have a close association with people. Studies show that they choose to live near areas of poor sanitation, thriving on associated small prey such as rodents and pigeons. The raptors also accept pieces of meat tossed to them by religious Muslims for whom kite-feeding is a centuries-old ritual. Yet, the main threats these birds face are human-made too: people sometimes collect kite chicks from nests for the illegal bird trade, while maintenance workers remove nests that pose a threat to electric wires or light poles. So is there a trade-off in how kites perceive people?
To find out, a team including researchers from Dehradun's Wildlife Institute of India surveyed 101 kite nests in the 1,500 square kilometres of Delhi city between 2013 and 2016. As they checked on each nest every 10 days for chicks, the team noted how the parent birds reacted to their presence. They scored each nesting pair on its intensity of nest-defense and compiled information from their earlier study to see if factors such as green cover and ritual feeding practices nearby influenced nest-defense.
They found that nest-defense by parent birds increased with the number of chicks in their nest and with the progression of the breeding season, suggesting that the adult birds increased their defense responses based on their parental investment (on the quantity and survival prospects of their chicks, which increased through the breeding cycle). Defense also intensified close to ritual-feeding areas that had higher human waste on the streets. Pairs that could invest in early aggressive defense during the incubation stage produced higher numbers of fledglings.
This ability of kites to discriminate between positive, neutral and negative human attitudes spells their urban success, said lead author Nishant Kumar (WII, and at the United Kingdom's University of Oxford).
“Such context-dependent habitation and aggression to humans has been shown in other animals such as Australian magpies and rhesus macaques too,” he said.
Therefore, coexistence with humans is often accompanied by “fine-grained, context-dependent strategies and trade-offs,” suggest the authors.