A recent study conducted by the respected journal The Scientific American has discovered that birds in urban environments sing louder today than they did in 1965.
The scientists who conducted the study of the Zonotrichia leucophyrs (the white-crowned sparrow) realized that the birds near to San Francisco's famed Golden Gate Bridge park are now singing at a much higher pitch than they did just forty-seven years ago. Bird experts believe that the animals have adapted to the loud traffic noises near to the popular tourist attraction and now sing more loudly to be heard over the din of urban noise pollution.
The study concludes that the change in behavior in the birds proves the theory that evolutionary processes can occur in a relatively short period of time, giving animals a chance to adapt to sudden environmental changes and improving a species chances at survival. The higher pitch singing allows for better communication between the birds in an urban setting, giving them the chance to be heard more clearly during the mating process.