Butterflies may be better indicators of the health of our environment than birds.
Roger Tory PetersonPenguins are an indicator of the health of our watery planet, and if they are unable to survive, we had better take notice or we might find our own survival threatened.
Roger Tory PetersonBirds ... are sensitive indicators of the environment, a sort of "ecological litmus paper," ... The observation and recording of bird populations over time lead inevitably to environmental awareness and can signal impending changes.
Roger Tory Peterson