Cognitive incapacitation: theoretical and methodological considerations

Worldwide, urban areas are spreading at massive rates. Simultaneously, urban agriculture is growing in importance. However, urbanization effects on functional biodiversity on farmland remain poorly studied, especially in urbanization hotspots of the global south. Here, we sampled birds on 36 farms across three seasons (one full year) and along two urbanization gradients in the Indian megacity Bangalore, using a paired site design to separate local and landscape effects of urbanization. At various spatial scales, including local and multiple landscape scales, we observed a consistent reduction in bird diversity as a result of urbanization. An increase of landscape-wide impervious surface area from 0% to 80%, lead to an average reduction of 50% of bird species and individuals, with open woodland species being the biggest losers. Invertebrate-feeding birds already experienced 60% losses with only 40% of impervious surface, particularly during the monsoon, i.e. the main cropping season, suggesting a great potential decrease in biocontrol services for farmland in urban areas. In conclusion, we documented high losses of farmland birds in an Indian megacity due to intense and rapid urbanization, which is generally little studied but can be currently observed in many other tropical countries.