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.

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

Not all is doom and gloom. We are beginning to understand the natural world and are gaining a reverence for life - all life.

Butterflies may be better indicators of the health of our environment than birds.

Birds, it must be admitted, are the most exciting and most deserving of the vertebrates; they are perhaps the best entre into the study of natural history, and a very good wedge into conservation awareness.

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.

Vultures are homely, but they clean up all the garbage and that's good. And they're elegant in the sky.