Study Finds Health Trade-Offs for Wildlife as Urbanization Expands
City living appears to improve reproductive success for migratory tree swallows compared to breeding in more environmentally protected areas, a new five-year study suggests. But urban life comes with a big trade-off – health hazards linked to poorer water quality. Researchers found that city-dwelling birds bred more nestlings because of warmer local temperatures. But they also had much higher levels of mercury in their blood – presumably from eating insects that spent their larval stages in contaminated water – than their counterparts breeding in less urban areas.
