I can recognize the calls of practically every bird in North America. There are some in Africa I don't know, though

Birds are indicators of the environment. If they are in trouble, we know we'll soon be in trouble.

Birds are an ecological litmus paper.

Birding, after all, is just a game. Going beyond that is what is important.

Birds ... 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.

The other creatures with which we share this world have their rights too, but not speaking our language, they have no voice, no vote; it is our moral duty to take care of them.

Penguins 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.