Higher adaptive tolerance with higher risk for sparrows living in airport environments

Abstract

Adjustments in flight initiation distance (FID) indicate how birds adapt to external environmental changes, including semi-natural ecosystems such as airports with regular disturbances. This study focused on sparrows (Passer montanus) as the research subject, because it is a dominant species with a high risk of bird strike events at airports. We investigated the FID and its influencing factors both inside and outside an airport compound to determine sparrows' vigilance and their adaptive adjustments to the airport environment. The FID of sparrows showed no significant variation between inside and outside the airport compound. However, a significant reduction of FID was exhibited during the breeding season. Group size showed a significant positive impact on the FID, somewhat supporting the many-eyes hypothesis, in which larger groups with more individuals may detect predators earlier. Additionally, the stimulus type and location influenced the effect of group size on FID, with most birds showing greater tolerance to vehicles than to humans, and being slightly bolder inside the airport than outside it. Overall, sparrows showed a higher tolerance to disturbance inside the airport compound and less vigilance to vehicles than to humans. Nevertheless, these adaptations may inadvertently form an ecological trap for bird populations around airports, exposing them to the dual threats of higher levels of raptor predation and the hazards of bird strikes. Thus multifaceted bird-scaring strategies and measures should be formulated to ensure flight safety and enhance avian survival during airport management.