Laura Erickson's For the Birds

The song of Scarlet Tanagers, which used to resonate through the summer forests of eastern North America, gets harder to detect each year. These brilliant red insect eaters are birds of the mature, unbroken hardwood and mixed forest. Some of them settle for second growth, and others for parcels of forest fragmented by roads and country homes, but most of the birds breeding in marginal habitat end up raising baby cowbirds instead of tanagers. Cowbirds don’t invade unbroken forest, which is why fragmentation plays such a crucial role in the disappearance of many songbirds. The worst affected are those, like the tanager, that migrate to the tropics, because their breeding season up here is so short. If their first brood is lost to raising a cowbird, they don’t get another chance before they have to head south. And then once they reach the tropics, from Panama and Columbia south to Bolivia, they often discover that their winter territory has been deforested.

Forest birds that migrate to the tropics are probably the ones facing the most critical declines in numbers. But other songbirds of North America are also suffering. Bobolinks and meadowlarks, once abundant throughout Wisconsin and Minnesota farmland, are disappearing. Native grassland sparrows are in serious trouble, too. Recent declines in birds of open country are due in large part to pesticide contamination. Not only does spraying poison them directly and contaminate their food, but it also has a long-term insidious effect, destroying the insects, grubs, and worm populations that they depend on.

House cats are another serious problem facing birds today. Cats are subsidized by their owners, and are farm more numerous than natural predators, especially in towns and farm country. Dr. Stanley Temple of the Department of Wildlife Ecology at the University of Wisconsin in Madison, has been conducting a long-term study into the effects cats have on bird populations. He finds that cats in rural Wisconsin are a primary factor in the decline of several species of songbirds. Another study indicates that the reduction in field mice from outdoor cats depletes the food supply for wintering hawks.

Then there are buildings, towers, picture windows, power lines, and other man-made obstructions. 20,000 songbirds were killed at a single TV tower in Eau Claire, Wisconsin, on a single foggy night in September 1957. Although that was clearly a unique disaster, another 40,000 were killed by the same tower on a two-day weekend 6 days later. Every day during spring and fall migration, birds crash into other structures. One white pelican even flew into a boat antenna in the Duluth harbor last autumn, and was mortally wounded.

Dr. Sidney Gauthereaux recently published a study in British Birds using weather radar data to conclude that between the 1960s and the 1980s, there has been a 50 percent decline in the number of birds migrating along the coast of the Gulf of Mexico.

Without question, our birds are in big trouble. We can “Don’t Worry, Be Happy,” like administration officials who’d like to write off the Northern Spotted Owl and the Mt. Graham Red Squirrel as mere inconveniences, or we can search for wise solutions to protect our irreplaceable natural legacy. The choice is ours.