Birds in cities are getting louder. New research from Hungary's Centre for Ecological Research reveals that some urban species are shifting their songs to higher frequencies and greater volumes, adapting to the relentless acoustic assault of traffic and construction. The finding adds to a growing body of evidence that cities fundamentally reshape animal behavior, not just where creatures live, but how they communicate, compete for mates, and survive. Scientists say the changes suggest birds may be struggling to maintain their evolutionary strategies in a world increasingly dominated by human noise.