THE eminent ornithologist Roger Tory Peterson once groused publicly about the time and effort the National Audubon Society invests in environmental issues, such as rapid population growth. From his perspective, these problems are extraneous distractions that prevent Audubon from devoting its full attention to the plight of birds.
That curiously narrow view exposed him as something of an ostrich, head so deep in the sand that he refused to acknowledge the impact of demographic growth on the habitat and food supply of his feathered friends. Anyone concerned about trends in bird species must be concerned about trends in human population. The reverse is equally true.
Birds are an accurate gauge of human conditions - the global equivalent of the canaries that were used to test coal mine shafts for dangerous air conditions. Birds can be readily tracked and studied and they react swiftly to shifts in environmental patterns. As Howard Youth points out in Worldwatch Institute's recently published ``Vital Signs 1994,'' declines in the world's bird species ``flag environmental dangers that imperil us as well as them.''
Birds and humans share the same life-support systems, Mr. Youth observes. As grasslands vanish in India and Pakistan, so do bustards and other birds that once thrived in these populous venues. As wetlands disappear, so do waterfowl that breed and feed in these ecosystems. The construction of outsized dams, such as those planned and under way in Turkey and India, pose a grave threat to birds by disturbing or destroying grasslands, wetlands, and forests.
Birds are also key participants in the ecological chain. Flowering shrubs and trees are pollinated by hummingbirds. The population growth of small rodents is checked by various birds of prey. The seeds of some trees are dispersed through the droppings of hornbills and other large fruit-eaters.
Tropical forests, repositories for so many of nature's wonders, are cut down at the rate of 100 acres per minute - the result of a combination of logging, the demand for grazing and farm land, and the need for fuel-wood and shelter for rapidly growing populations. At that rate, the world's tropical forest cover may virtually vanish within the next 10 to 20 years. These same tropical forests are home to at least 3,500 bird species.
Seventy percent of the world's bird species are declining - includ-ing 1,000 under immediate threat of extinction. Since the 17th century only 150 species and subspecies of birds have been lost.
The extinction of a bird species amounts to more than the silencing of the sweet nocturnal song of the nightingale; more than never witnessing an eagle spread its great wings and soar skyward, defining strength, grace, and freedom. For birds are, in a very real sense, humanity's harbingers; their destiny is ours. The Opinion/Essay Page welcomes manuscripts. Authors of articles we accept will be notified by telephone. Authors of articles not accepted will be notified by postcard. Send manuscripts by mail to Opinions/Essays, One Norway Street, Boston, MA 02115, by fax to 617 -450-2317, or by Internet E-mail to OPED@RACHEL.CSPS.COM.