In more and more places in the United States, birds are disappearing. One woman from Illinois wrote of the absence of birds after the elm tress of her town were sprayed with DDT. Another woman wrote from Alabama describing the sharp drop in birds in an area that had been a bird sanctuary for more than fifty years. During the same time she was writing, other reports came in from the Southern states of Mississippi, Louisiana, and Alabama. People were reporting the shocking drop in the number of bird sightings in places where they had previously been abundantly present.
What happened to the robin is a good case in point. The survival of the robin is linked to the American elm tree, a tree popular in cities for landscaping. In 1930 Dutch elm disease was inadvertently imported into the U.S. from Europe. It is a fungus disease which invades the tree and spreads by spores. It is spread among trees by elm bark beetles. People have concentrated efforts on killing the carrier insect in order to stop the spread of the disease. In the Midwest and New England where the elm is so abundantly used in cities, intensive insecticide spraying has gone one.
Two ornithologists (bird scientists) from Michigan State University found evidence of the link between the deaths of robins and the spraying of elm trees with insecticide. One of them had been doing his doctoral studies in robin population just as the spraying campaign began on his campus. He found the robin population had plummeted drastically just after the spraying and began studying why. The elms were sprayed during one spring and the following spring, robins returned to the campus and the city on their migratory path. Suddenly, however, people began finding them dead all over campus. Every spring, this pattern was repeated. New birds would fly in and soon they would be found dead. The two scientists discovered that the birds were dying of insecticide poisoning. They died with all the symptoms of poisoning: loss of balance, tremors, convulsions and then death. The scientists found that the birds were dying of insecticide poisoning because they were eating earthworms contaminated by the poison.
Another scientist at the Illinois Natural History Survey traced the cycle of the poison. The trees were sprayed twice a year with heavy doses of the insecticide DDT. When the leaves fell in the autumn, the leaves were mulched by earthworms. Earthworms accumulated and concentrated DDT in their systems and then birds ate the earthworms. Even when birds don't die from exposure to DDT, they become sterile. Mammals are also affected. Raccoons eat earthworms as do opossums. Shrews and moles eat them and then themselves are eaten by owls and other predators. Hawks and owls were found in the last stages of death, having convulsions. Not only ground eaters, but also tree top eaters are hurt by the insecticide spraying. Birds which feed on the insects of trees are killed. In one year, a late spring delayed spraying so that it coincided with an exceptionally heavy wave of warbler migration. Nearly all of these birds were killed. In one place in Wisconsin, more than a thousand warblers were usually seen in the spring migration time. After a spraying, only two were to be found.
Not only are birds affected by eating contaminated worms and insects. They are also affected by a loss of food when these creatures are killed off wholesale. One observer in Wisconsin wrote of the disappearance of the beautiful bird, the phoebe. He added, "It is tragic. I can't bear it." Many of these birds which eat insects are helpful to the health of trees. When the birds are gone, the insects become too strong and eat the tree. Birds play a crucial role in pest control.
People are becoming more and more aware of the death of the birds in their communities. Often, citizens are much more clear thinking about the use of insecticides that the city and government officials who are responsible for the spraying campaigns. People are writing in to newspapers asking why insecticides are still being used when they are so dangerous and when they are so ineffective in the long run. They are also recognizing the fact that even though elms are well loved trees, they aren't more important than the health of the ecology.
These people would be even more concerned if they knew exactly how ineffective spraying is. In some places, spraying actually increases the rate of death of elm trees. This result happens because spraying kills all the natural enemies of the elm disease. More troubling is the fact that the Midwestern towns could have found a perfectly sound method of controlling the disease by looking to the example of eastern cities, cities that were hit by the disease first. In New York, city officials began a program of sanitation: clearing away all dead and diseased trees and limbs as soon as they were spotted. As a result, they contained the disease so that it became insignificant. The same program was applied n Syracuse. Before the program, the city of Syracuse lost 3,000 elms. After the program, it lost less than one percent of the trees. The sanitation method is not only effective, it's also cheaper than spraying. Cities would eventually have to clear away dead and dying trees and limbs anyway. If they do it more promptly, they're not spending any more money than would normally be in their budgets.
Another long-term solution would be to use a variety of trees instead of planting only one kind. That way, if something attacks one variety, it will be unlikely to wipe out all the landscaping trees of a town or city.
Another American bird is also on the verge of distinction: the American eagle. One group of eagles have been intensively studied. They are those living on the Florida coast. One ornithologist banded more than 1000 eagles from 1939-49. When he first began banding birds, he would find 125 active nests and would band 150 young eagles. In 1947, the number of eagles began to decline. He found over the next ten years that many nests never had eggs in them and that often, the eggs that were viable hatched birds that died soon afterward. By 1958, this scientist searched over 100 miles of coastline before finding and banding only one eaglet.
A curator of a Florida bird sanctuary continued the work of documenting the loss of eagles in Florida. The eagles that come through the sanctuary have been counted over the years and these numbers tell the story of the eagles' destruction. From 1935 to 1939, 40 per cent of the eagles were yearlings. Between 1955 and 1959, only 20 per cent were yearlings. Other sanctuaries report similar findings.
It's hard to study the eagles directly to find out what the cause of their extinction is, but scientists can study other bird species and then apply those results to the situation of eagles. One scientist studied the affects of insecticides on quail and pheasants. He found that exposure to DDT and other chemicals sometimes doesn't seem to affect the birds, but later, the affects are seen in the birds' sterility. They either don't produce any eggs, or the poison is stored in the egg yolks and the eggs never hatch. It's very difficult to apply these findings to eagles, but the evidence is compelling that insecticides are responsible for the extinction of eagles.
Other countries have also experienced shocking numbers of bird deaths. In France, partridges disappeared after vine stumps were treated with arsenic. In England, the problem occurs with insecticide treated seed. Huge numbers of birds eat these poisoned seeds and die. Not only birds, but foxes have also died from the insecticides. Since foxes are necessary for keeping the numbers of rabbits down, people have begun to call for a ban on these insecticides.
In this chapter, Rachel Carson shows another step in the line of attack of insecticides. She's described their affect on the soil, the plant life, other forms of life. Here, she describes insecticides' destruction of wild birds. Here as well as above, Carson uses two dominant means of persuasion: logical and ethical. She describes the scientific methods used to determine the link between insecticide spraying and bird deaths. She also reminds the reader over and over of the value of wild birds in the world as members of ecology we all live in.