Chapter 9 Eight no more birds sing

Now in the United States, more and more places have no birds flying to herald the spring; when you get up early in the morning, you can hear the beautiful singing of birds everywhere, but now it is just very quiet.The song of the birds has suddenly been silenced, and the color, beauty and joy that birds have given to our world has been neglected because some places have not yet felt its role, so that now the birds are quietly extinct. In desperation, a housewife wrote from Herstal, Illinois, to Robert Cushman Maffey, curator emeritus of birds at the American Museum of Natural History (and a world-renowned ornithologist): , have been spraying elms for several years. (This letter was written in 1958) When we moved here six years ago, there were so many birds that I started keeping them. Throughout the winter Cardinals, chickadees, woolly birds and nuthatches fly here in endless streams; and in summer, cardinals and tits return with their smaller birds.

After a few years of DDT spraying, the town is almost free of robins and starlings; I haven't seen a chickadee in my aviary for two years, and this year the cardinals are gone; The nesting birds appear to consist of only a pair of pigeons and possibly a litter of catbirds. It is not easy for me to tell children that birds are killed when they are taught in school that federal law protects birds from being killed.Will they come back?The child still asked, but I had no words to answer.The elms are dying, and so are the birds.Are measures being taken?What can be done?What can I do? "

In the year after the federal government began a massive fire ant spraying program, an Alabama woman wrote: "This place of ours has been a true sanctuary for birds for the better part of a century. Last October, We all noticed that there were more birds here than before. However, suddenly, in the second week of August, all the birds disappeared. I used to get up early every day to feed my beloved pony already the foal's mare, but not a single bird's cry was heard. The sight was bleak and disturbing. What have people done to our wonderful world? Finally, until five months later, there was a The blue jays and wrens appeared."

We had other equally sombre reports from Mississippi, Louisiana, and far southern Alabama during the fall the woman is referring to.The Field Chronicle, a quarterly journal published by the National Atopian Society and the U.S. Fish and Wildlife Service, documents the appalling phenomenon of dreaded voids in the country devoid of any birds. Field Chronicles is compiled from reports written by experienced observers who have spent many years in the field in specific areas and have an unrivaled wealth of knowledge of normal bird life in those areas .One spotter reported seeing no birds at all for long stretches of his drive that fall in southern Mississippi. Another observer at Bayton Rdger reported that the feed she had placed was left there "without the birds for weeks"; but the boughs were still laden with berries. Another report says that his window "used to be a speckled picture of forty or fifty cardinals and large flocks of other birds, but now It's rare to see a bird or two appear. "West Virginia University professor Morse Brooks, an authority on Appalachia's birdlife, reports that "the decline in West Virginia's bird population is mind-boggling."

Here is a story that may serve as a symbol of the bird's tragic fate--a fate that has conquered some species and threatens all birds.This story is known as the Mockingbird's Tale.For millions of Americans, the first robin means winter's rivers have thawed.The arrival of the robin was reported in the papers as a distraction, and was eagerly announced at dinner.With the gradual arrival of migratory birds, the forest began to turn green, and thousands of people listened to the first song of the dawn chorus of robins in the early morning.Now, however, everything has changed, and even the return of the birds is not taken for granted.

The survival of the robin, and indeed many other birds, seems to be closely tied to the American elm.From the Atlantic coast to the Rocky Mountains, the elm has been a part of the history of a thousand cities and towns, adorning streets, cottages and schoolyards with stately green archways.The elm is now infested with a disease which has spread to all elm-growing regions, and the disease is so severe that experts admit that all efforts to cure the elm will be futile at last.Losing the elm is sad, but it would be doubly sad if, in the futile effort to save the elm, we threw the vast majority of our birds into the darkness of destruction.And this is what threatens us.

The so-called Dutch elm disease was introduced to the United States around 1930 when elm knots for the paneling industry were imported from Europe.The disease is a fungal disease; the fungus invades the water ducts of the tree, its spores spread through the flow of sap, and cause the twigs to wither and kill the elm by having a poisonous exudate and clogging action .The disease is spread from diseased trees to healthy trees by elm bark beetles.The channels dug by the insect under the dead bark are later contaminated with invading fungal spores, which in turn stick to the beetle and are carried by the beetle everywhere it flies.Efforts to control this elm disease have always depended in large part on the control of the insect vectors.So in the American Midwest and New England, where the American elms are concentrated, widespread spraying village by village has become a routine.

What does this spraying mean for bird life, especially for robins?The first clear answer to this question was given by George Wallace, a professor at Michigan State University, and one of his graduate students, John Miner.When Mr. Miner began his doctoral dissertation in 1954, he chose a research topic on robin populations.This was entirely a coincidence, because at that time no one suspected that the robin was in danger.But just as he was doing this research, something happened which changed the nature of his subject and deprived him of an object of study. Spraying for Dutch elm disease began in 1954 in a small area on a university campus.The following year, campus spraying was expanded to include Eastland Star City (where the university is located), and not only gypsy moths but also mosquitoes were sprayed in the local program as well.The chemical rain has increased to the point of pouring down.

In 1954—the first year of the first small spraying—everything seemed to be going well.The following spring, migrating robins began returning to campus as usual.Like the bluebells in Tomlinson's essay "The Lost Woods," they "expect no misfortunes" when they reappear in their familiar places.However, it soon became apparent that something was not quite right.Dead and dying robins began to appear on campus.Birds are almost gone where they used to peck and roost in clusters.Few birds built new nests, and few chicks emerged.This was repeated monotonically over the next few springs.The sprayed area has become a lethal trap that can wipe out a migrating robin population in just a week.Then newcomers fall into the trap again, adding to the number of doomed birds that can be seen all over the campus, all trembling in their death struggle.

"Campus has become a graveyard for most robins trying to find shelter in the spring," says Professor Wallace. But why?At first he suspected some nervous system disorder, but it soon became apparent that "despite the assurances of those who use insecticides that their sprays are 'no harm to birds,' the robins do Died of pesticide poisoning, the robin exhibited the familiar symptoms of loss of balance, followed by tremors, convulsions and death." Some facts suggest that the poisoning of robins is not due to direct contact with insecticides, but indirectly due to eating earthworms.Earthworms on campus were accidentally used to feed mole crickets used in a research project, and all the mole crickets soon died.A snake kept in a lab cage shook violently after eating the worms.However earthworms are the main food of robins in spring.

The mystery of the doomed robin's death was soon answered by Dr. Roe Buck of the Illinois Institute of Natural History in Urbana.Barker, whose book was published in 1958, found an intricate circle of events—the fate of the robin linked to the elm through the action of the earthworm.The elms are sprayed in the spring (usually at a rate of 2-5 pounds of DDT per 50 feet of tree, equivalent to 23 pounds of DDT per acre of heavily elm-heavy areas).It is often sprayed again in July, and the concentration is half of the previous time.A powerful sprayer sprays a poisonous water dragon up and down the tallest trees in the Huai River, which not only directly kills the bark beetle it was meant to destroy, but also kills other insects, both pollinating insects and those that prey on other insects Spiders and beetles.The poison forms a sticky film on the leaves and bark that rain cannot wash away.In autumn, the leaves fall to the ground, accumulate in a moist layer, and begin the slow process of becoming part of the soil.In the process they are assisted by earthworms, which eat the detritus of the leaves, as elm leaves are one of their favorite foods.While eating the leaves, the earthworms also swallowed the pesticides, which accumulated and concentrated in their bodies.Dr. Barker discovered deposits of DDT in the digestive tracts, blood vessels, nerves, and body walls of earthworms.Undoubtedly, some earthworms could not resist the poison and died, while other surviving earthworms became "biological amplifiers" of the poison.Another link in the cycle occurs in the spring, when the robins arrive.It takes only eleven large earthworms to deliver a lethal dose of DDT to a robin.Eleven earthworms are only a small part of a bird's daily food intake, and a bird can eat 10 to 12 earthworms in a few minutes. Not all robins ingested lethal doses, but another consequence, as surely as the inevitable poisoning, could have led to the extinction of the species.The shadow of sterility hangs over all birds, and its potential threat extends to all living things.There are now only two or three dozen robins to be found each spring on MSU's entire 185-acre campus; compared with a rough estimate of 370 birds here before spraying.Every robin nest observed by Miner in 1954 produced chicks.By the end of June 1957, there would have been at least 370 juveniles (a normal proxy for the number of adults) foraging on the campus had it not been sprayed, yet Miner has now found only one robin.A year later, Professor Wallis reported: "During the spring and summer [of 1958] I have not seen a fledged robin anywhere on campus, and I have never heard of anyone seeing one Mockingbird." Of course, part of the reason no chicks are born is because one or both robins in a pair die before the nesting process is complete.But Wallis has a remarkable record that points to something more ominous—the fact that the birds' reproductive capacity has been destroyed.For example, he recorded that "robins and other birds built nests without laying eggs, and the other eggs did not hatch chicks. We recorded a robin that lay confidently on the nest for 21 days, but No chicks hatched. The normal nesting time is 13 days....Our analysis found high concentrations of DDT in the testes and ovaries of nesting birds.” Wallace, 1960 Told Congress: "The testes of ten male birds contained 30-109 parts per million of DDT, and the egg follicles of the ovaries of two female birds contained 150-200 parts per million A DDT of eleven." Studies in other regions have since begun to find the situation equally worrying.Professor Yousuf Heck of the University of Wisconsin and his students reported that the death rate of robins was at least 86-88% after a careful comparative study of sprayed and unsprayed areas.The Crane Creek Institute of Science near Blossom Hill, Michigan, which made an effort to estimate the extent of bird losses from elm spraying, requested in 1956 that all birds thought to have died of DDT poisoning be sent to the institute Perform assay analysis.This request met with a totally unexpected response: within a few weeks, the long-unused instruments in the Institute were run to maximum workload, so that other samples had to be rejected. In 1959, a thousand poisoned birds were reported or handed over to one village or town alone.While robins were the main victims (one woman called the institute to report that 12 robins were lying dead on her lawn when she called), 63 other species of birds were included Children were also tested at the institute.The robin was only part of a destructive chain reaction involving elm spraying, and the elm spraying program was only one of many spraying programs that covered the ground with poison.Some 90 species of birds suffered severe casualties, including those most familiar to suburbanites and amateur nature lovers.In some towns that were sprayed, the number of nesting birds was generally reduced by as much as 90 percent.As we shall see, a wide variety of birds are affected—ground-feeding birds, treetop-foraging birds, bark-feeding birds, and birds of prey. There is every reason to suppose that all birds and mammals that feed primarily on earthworms and other soil organisms are as threatened as the robin's fate.About 45 species of birds feed on earthworms.One such species is the woodcock, which has been wintering in the South, which has recently been heavily sprayed with heptachlor.Two important discoveries have now been made in the woodcock.In the New Brunswick hatchery, the juvenile population was significantly reduced, and analysis of mature birds showed high levels of DDT and heptachlor. There have been disturbing records of mass die-offs of more than 20 species of ground-feeding birds.The birds' food -- worms, ants, maggots, or other soil organisms -- is already poisonous.These include three species of thrushes - the olive-backed bird, the jasper and the hummingbird Finches have the most beautiful song among birds.And the sparrows, the song sparrows, and the white-throated jays, who skimmed the thick undergrowth of the woodland and rustled among the fallen leaves, were also victims of the spraying of the elms. Likewise, mammals are vulnerable to being directly or indirectly caught up in this chain reaction.Earthworms are an important food item for raccoons, and kangaroos often eat them in spring and autumn.Subterranean burrowers such as gophers and moles also prey on some earthworms, which may then pass the poison on to birds of prey such as owls and barn owls.In Wisconsin, several owls died after spring rains, possibly poisoned by eating earthworms.Some hawks and owls have been found in convulsions - among them the long-horned owl, hooting owl, red-shouldered hawk, sparrowhawk, moor hawk.They may have died from secondary poisoning by eating birds and mice that had accumulated the pesticide in their livers and other organs. The birds that suffer are not just those that hunt on the ground, or the raptors that prey on birds that are at risk from the spraying of elm leaves.The elves of those woodland areas--the red-crowned and golden-crowned wrens, the tiny mosquito-catchers, and the many songbirds that flock the woods in spring to a gleam of life--are all on the branches foraging insects from the leaves. Birds of prey have disappeared from heavily sprayed areas. In the late spring of 1956, due to the postponement of the spraying time, the spraying coincided with the migration climax of a large group of songbirds.Nearly all songbirds that flew into the area were mass-killed.At Whitefish Bay, Wisconsin, where at least a thousand migratory hickory warblers are seen in a normal year, observers saw only two in 1958, after the elms were sprayed.The list grows with reports of bird deaths from other villages and towns, and among the songbirds killed by the spray are some that fascinated all who saw them: the black and white, the goldfinch, the magnolia The jay and the cape may, the roast bird whose song echoes in the woods of the first month, the burnt jay with flaming colors on its wings, the sorrel jay, the Canada jay and the black-throated green jay.The branch-foraging birds were either directly affected by eating the poisonous insects, or indirectly, by lack of food. The loss of food also hits the hovering swallows hard, hunting for aerial insects like herrings scrambling to catch plankton in the sea.A Wisconsin naturalist reported: "Swallows have been terribly damaged. Everyone is complaining that there are so few swallows now compared with four or five years ago. Only four years ago the sky above us The birds were once full of flying swallows, and now we rarely see them...this may be due to both the scarcity of insects by the spraying, or the poisoning of the insects." Referring to other birds, the observer wrote "Another notable loss is the flycatcher. Flycatchers are hard to see everywhere, but the young, hardy common flycatcher is nowhere to be seen anymore. I saw one this spring and only one last spring. Wisconsin Other birders in the state have the same complaints. I used to have five or six pairs of cardinals and now I have none. Wrens, robins, catbirds and owls are in our garden every year and now there is none. There is no bird song in the summer mornings. Only vermin, pigeons, starlings, and English swallows remain. It is so miserable that I cannot bear it." The regular spraying of elms in the autumn, which gets the poison into every little crevice of the bark, probably accounts for the drastic decline in the numbers of the chickadees, nuthatches, chipmunks, woodpeckers, and brown woodpeckers. .During that winter of 1957 and 1958, Professor Wallace noticed for the first time in many years that chickadees and nuthatches were missing from his aviary.He later concluded from the three nuthatch found a sad fact showing causality: one nuthatch was pecking at the elm tree, and the other was dying from the poisoning disease characteristic of DDT , the second one is dead.It was later determined that 226 parts per million of DDT was present in the tissues of the dead nuthatch. The feeding habits of all these birds not only make them especially vulnerable when insects are sprayed, but are extremely costly, economically and in other less obvious ways.For example, the summer diet of the white-breasted nuthatch and the brown woodpecker includes eggs, larvae, and adults in large numbers of insects that are also harmful to trees.Three-quarters of the chickadee's diet is animal, including a variety of insects in all stages of growth.The foraging patterns of the titmouse are described in The History of Life, the immortal book on North American birds: "When a flock of titmouse comes to a tree, each bird carefully searches the bark, twigs and trunk to find a little food (spider eggs, cocoons, or other hibernating insects)." Numerous scientific studies have confirmed the decisive role played by birds for insect control in various situations.Woodpeckers are the main controller of the Engelmann needle-fir beetle, reducing the beetle population from 55% to 2%, and play an important role in controlling cod moth in apple orchards.Chickadees and other winter lingering birds can protect orchards from damage such as inchworms. But what happened in nature can no longer be done in today's chemical-soaked world, where spraying kills not only insects but their arch-enemies, birds .As usual, when the insect populations recovered later, there were no birds to check the increase.As O. J. Clomey, curator of birds at the Milwok Public Museum, wrote in the Milwok Daily: "An insect's worst enemy is other predatory insects, birds, and some small mammals, but DDT but kills everything indiscriminately, including nature's own guards and policemen... In the name of progress, shall we ourselves become the victims of our diabolical control of insects, which can only be achieved temporarily The ease of life, will fail later. How will we control new pests by then? The elm trees will be destroyed, and nature's guard birds will die due to poisoning. At that time, these pests will eat what is left species." Mr. Clomey reports that calls and letters reporting dead and dying birds have been on the rise in the years since spraying began in Wisconsin.These inquiries tell us that the birds in the sprayed areas are dying. Clomi's experience is shared by ornithologists and observers at most research centers in the Midwest, the Crane Creek Institute in Michigan, the Natural History Survey in Illinois and the University of Wisconsin.A glance at the mail columns of almost any newspaper in a district where spraying is being carried out will clearly reveal the fact that not only are the residents aware and outraged, but they are more active than the officials who ordered the spraying. Have a deeper understanding of the hazards and irrationality of spraying."I fear the day is now approaching when many of the beautiful birds in our backyard will die," wrote one Miwok woman. Disappointing and infuriating because it clearly fell short of what this massacre was intended to achieve... In the long run, can you save the trees without saving the birds? In nature's organism Aren't they interdependent? Isn't it possible to restore balance to nature without destroying it?" In other letters, the opinion is expressed that the elm, though a majestic and tall tree, is not the "divine bull" of India, and cannot be used as a justification for endless campaigns aimed at destroying all other forms of life.Another woman in Wisconsin wrote: "I've always loved our elm tree that stands like a signboard in the field, however we have many other types of trees...we have to save our birds too. Who can imagine how gloomy and lonely a spring is without the song of the robin?" Do we want birds?Still want elm?In the eyes of ordinary people, choosing one of the two seems to be a very simple matter.But in fact, the problem is not so simple.One of the plethora of chemical control ironies is that if we continue on the path we're on now, we're likely to end up with neither birds nor elms.Chemical spraying is killing the birds but not saving the elms.The illusion that the sprayer will save the elms is a dangerous will-o'-the-wisp that is leading one village after another into a morass of enormous expenditure without lasting effect.Greenwich, Connecticut has been regularly sprayed with pesticides for ten years.But a year of drought brought conditions especially favorable for the beetles, and elm mortality rose tenfold.Dutch elm disease first appeared in 1951 in Oberna, Illinois, home to the University of Illinois. Chemical spraying was carried out in 1953.By 1959, despite six years of spraying, school grounds had lost 86 percent of their elms, half of which were victims of Dutch elm disease. In Toledo, Ohio, the same circumstances prompted J. A. Sweeney, the Superintendent of the Forestry Department, to adopt a realistic approach to spraying.There began spraying in 1953 and continued until 1959.Mr. Sweeney observed that the great spread of cotton maple erythritis was much worse after the spraying, which had been recommended by "books and authorities."He decided to check for himself the results of spraying for Dutch elm disease.What he found surprised himself.He found that the only areas where we could control treatment in Toledo were those where we took decisive steps to remove diseased trees or plant trees, whereas where we relied on chemical spraying, elm disease was not controlled.And in the United States, where no treatment has been done, elm disease has not spread as rapidly as the city.This fact shows that chemical spraying has destroyed all natural enemies of elm disease. "We're giving up spraying for Dutch elm disease. That puts me at odds with those who support USDA's claims, but I have the facts in my hand and I'm going to put them in a difficult position." It is difficult to understand why these Midwestern towns (which have only recently experienced elm disease) have so recklessly engaged in ambitious and expensive spraying programs without reporting to people who already knew about the problem. Do some research in the area.Example: New York State certainly has a long experience in controlling Dutch elm disease.Diseased elms entered the United States from New York Harbor around 1930, and the disease was introduced with it.New York State still maintains an impressive record of stopping and eradicating this disease.However, this control does not rely on drug spraying.In fact, the state's Agricultural Establishment Program does not recommend spraying as a method of village control. So how did New York State achieve such good results?From the early days of the struggle to preserve the elms until today, the state has relied on a rigorous defense of swiftly removing and destroying all diseased or infected trees.Some initial results were disappointing, but this was due to an initial failure to realize that not only diseased trees but all elms in which the beetles were likely to lay their eggs should be destroyed.Infested elms that are cut down and stored for firewood can produce many infested beetles unless they are burned before spring.Mature beetles that emerge from hibernation and forage in late April and May can spread Dutch elm disease.Entomologists in New York State know empirically what kinds of wood the beetles lay their eggs in are of real importance for disease transmission.By concentrating these dangerous timbers, it will be possible not only to obtain good results, but also to keep the cost of the defense program low.By 1950, New York City's Dutch Elm House had reduced the incidence to 0.2 percent of the city's 55,000 elms. In 1942, a defensive campaign was launched in Westchester County.In the subsequent 14 years, the average loss of elms was only 0.2% per year.The city of Buffalo, with its 185,000 elms, has had an excellent record of controlling the disease, with losses totaling only 0.3% in recent years due to defense efforts.In other words, at this rate of loss, it would take 300 years for all the elms in Buffalo to be lost. What happened at Syracuse in eastern Sicily is particularly memorable.There were no effective plans put into effect until 1957.Between 1951 and 1956 Syracuse lost nearly 3,000 elms.At that time there was a vigorous campaign under the direction of H. C. Millet of the New York State College of Forestry to eradicate all diseased elms and all possible sources of the elm-eating beetle.The rate of loss has now dropped to 1% per year. When it comes to controlling Dutch elm disease, New York State experts emphasize the economics of a preventative approach."In the vast majority of cases the actual cost is economical," says J. G. Mathersi of the New York State Agricultural College. "As a precaution against property damage and personal injury, if the situation is a dead or injured branches, the branch will eventually have to be removed. If it is a pile of wood, it should be used up before spring, the bark can be stripped, or the wood can be stored in a dry place. For In the case of dying or dead elms, the rapid removal of diseased elms to prevent the spread of Dutch elm disease costs no more than later costs, since most dead trees in large urban areas end up in Removed." Provided sensible measures are taken, combating Dutch elm disease is not entirely hopeless.Once Dutch elm disease has stabilized in a colony, it cannot be eradicated by any means now known except to take protective measures to keep them within limits, rather than those which are ineffective and cause misery for the lives of the birds. method of destruction.Other possibilities exist in the field of forest genetics, where experiments offer hope of developing a hybrid elm resistant to Dutch elm disease.The European elm is very hardy and many of these trees have been planted in the Washington Columbia area.Dutch elm disease was not found in these European elms even when urban elms were overwhelmingly affected by the disease.An emergency silviculture program is urgently needed to replant trees in towns that are losing large numbers of elms.It is important that while these plans may have included the hardy European elm, they should have focused more on building species diversity so that future epidemics cannot deprive a town of all the trees.The key to a healthy plant or animal community is, as British ecologist Charlie Eldon put it, "maintenance of diversity".What is happening now is largely the result of the biological simplification of past generations.Somehow as far as a generation ago, no one knew that planting a single species of tree on a large tract of land could spell disaster.So all the towns lined their streets and parks beautified with elms; and when the elms are dead today, so are the birds. Like the robin, another American bird that looks set to become extinct is the national symbol, the eagle.Eagle populations have declined alarmingly over the past decade.It turns out that there are factors at work in the eagle's environment that have actually destroyed the eagle's ability to reproduce.It's impossible to know exactly what was the factor, but there is some evidence that pesticides are to blame. The most thoroughly studied hawks in North America have been those that nest along the Florida west coast from Dampa to Fort.A retired Winnipeg banker, Charlie Brobbe, gained fame in ornithology for tagging more than 1,000 baby bald eagles between 1939 and 1949. (Only 166 hawks had been tagged in the entire history of bird tagging prior to this.) Mr. Brober tagged the young eaglets during the winter months before the hawks left their nests.Later rediscoveries of tagged birds indicate that these Florida-born hawks flew along the coastline north into Canada and as far as Prince Edward Island; however these hawks had previously been thought to be non-migratory.They returned south in the fall, and their migrations were observed from such a vantage point as the top of Hawker Mountain in eastern Pennsylvania. During Mr. Broler's first years of tagging hawks, he regularly found 125 nests with birds in a year's time on the stretch of coast he had chosen for his study.About 150 eaglets are tagged each year.In 1947 the number of kitty births began to decline.Some nests no longer contained eggs, and others that contained eggs did not hatch.Between 1952 and 1957, nearly 80% of the litters had no chicks.In the last year of this period, only 43 nests were still inhabited by birds.Among them, 7 nests hatched young birds (8 young eagles); 23 nests contained eggs, but no young eagles hatched; 13 nests were only used as resting places for large eagles to forage without eggs. In 1958, Mr Broler spotted and tagged a kitty after trekking 100 miles along the coast.In 1957, eagles could also be seen in 43 nests.At this time, it was rare to see, and he only saw big eagles in 10 nests. Although Mr. Broler's death in 1959 ended this valuable continuum of systematic observations, reports by the Atopian Society in Florida, as well as the states of New Jersey and Pennsylvania, confirmed a trend that likely forced We had to find a new national symbol.Maurice Brown (curator of Hawk Mountain Game Reserve) was particularly notable for his reporting.霍克山是宾夕法尼亚州东南部的一个美丽如画的山脊区，在那儿，阿巴拉契亚山的最东部山脊形成了阻挡西风吹向沿海平原的最后一道屏障。碰到山脉的风偏斜向上吹去，所以在秋天的许多日子里，这儿持续上升的气流使阔翅鹰和鹫鹰不需要花费气力就可以青云直上，使它们在向南方的迁徙中一天可以飞过许多路程。在霍克山区，山脊都汇聚在这里，而岭中的航道也是一样在这里汇聚。其结果是鸟儿们从广阔的区域通过这一交通繁忙的狭窄通道飞向北方。 莫瑞斯·布朗作为禁猎区的管理人在他二十多年的时间里，他所观察到并实际记录下来的鹰比任何一个美国人都多。秃鹰迁徙的高潮是在八月底和九月初。这些鹰被认为是在北方度过夏天后返回家乡的佛罗里达鹰。(深秋和初冬时，还有一些大鹰飞过这里，飞向一个未知的过冬地方，它们被认为是属于另一个北方种的。)在设立禁猎地区的最初几年里，从1935年－1939年，被观察到的鹰中有40%是一岁大的，这很容易从它们一样的暗色羽毛上认出来。但在最近几年中，这些未成熟的鸟儿已变得罕见了。在1955年一1959年间，这些幼鹰仅占鹰总数的20%；而在1957年一年中，每32只成年鹰里仅有一只幼鹰。 霍克山的观察结果与其他地方的发现是一致的。一个同样的报告来自伊利诺斯州自然资源协会的一位官员爱尔登·佛克斯。可能在北方筑巢的鹰沿着密西西比河和伊秘诺斯河过冬。佛克斯先生1958年报告说最近统计了59个鹰中仅有一只幼鹰。从世界上唯一的鹰禁猎区——撒斯魁汉那河的蒙特·约翰逊马上出现了该种类正在灭绝的同样征候。这个岛虽然仅在康诺云格坝上游区8英里，离兰卡斯特郡海岸大约半英里的地方；但它仍保留看它原始的洪荒状态。从1934年开始，兰卡斯特的一个鸟类学家兼禁猎区的管理人荷伯特·H·伯克教授就一直对这儿的一个鹰巢进行了观察。在1935年到1947年期间，伏窝的情况是规律的，并且都是成功的。从1947年起，虽然成年的鹰占了窝，并且下了蛋，但却没有幼鹰出生。 在蒙特·约翰逊岛上的情况与佛罗里达一样，流行着同样的问题——一些成年鸟栖息在窝里，生下了一些蛋，但却几乎没有幼鸟会出现。要寻找一个原因的话，看来只有一种原因可以符合所有的事实，即鸟儿的生殖能力由于某种环境因素而降低，以致于现在每年几乎没有新的幼鸟产生来传种接代了。 由美国鱼类及野生物服务处的著名的詹姆斯·大卫博士所进行的多种实验显示出在其他鸟类中确有同样的情况正在人为地产生着。大卫博士所进行的一系列杀虫剂对野鸡和鹌鹑影响效果的经典试验确证了这样一个事实，即在DDT或类似化学药物对鸟类双亲尚未造成明显毒害之前，已可能严重影响它们的生殖力了。鸟类受影响的途径可能不同，但最终结果总是一样。例如，在喂食期间将DDT加入鹌鹑的食物中，鹌鹑仍然活着，甚至还正常地主了许多蛋；但是几乎没有蛋能孵出幼鸟来。大卫博士说：“许多胚胎在孕育的早期阶段发育得很正常，但在孵化阶段却死去了。”这些孵化的胚胎中有一半以上是在五天之内死掉的。在用野鸡和鹌鹑共同作为研究对象的实验中，假若在全年中都用含有杀虫剂的食物来饲养它们，则野鸡和鹌鹑不管怎样也生不出蛋来。加利福尼亚大学的罗伯特·路德博士和查理·捷那雷博士报告了同样的发现。当野鸡吃了带狄氏剂的食物时，“蛋的产量显著地减少了，小鸡的生存也很困难。”根据这些作者所谈，由于狄氏剂在蛋黄中贮存，由于狄氏剂在孵卵期和孵出之后被逐渐同化而给幼鸟带来了缓慢的，但却是致死的影响。 这一看法得到了华莱士博士和一个毕业学生R·F.伯那德的最新研究结果的有力支持，他们在密执安州立大学校园里的知更鸟身上发现了高含量的DDT。他们在所检验的所有雄性知更鸟的睾丸里，在正在发育的蛋囊里，在雌鸟的卵巢里，在已发育好但尚未生出的蛋里，在输卵管里，在从被遗弃的窝里取出的尚未孵出的蛋里，在从这些蛋内的胚胎里，在刚刚孵出但已死了的雏鸟里都发现了这种毒物。 这些重要的研究证实了这样一个事实，即一旦使生物脱离与杀虫剂初期接触，杀虫剂的毒性也能影响下一代。在蛋和给与发育中的胚胎以营养的蛋黄里的毒物贮存是致死的真正原因，这也足以解释了为什么大卫看到那么多鸟儿死在蛋中或是孵出后几天内就死去了。 当将这些研究实验应用到鹰上时遇到了几乎无法克服的困难，然而野外研究正在佛罗里达州、新泽西州和其他一些希望能够对发生在这么多鹰中的明显不孕症找出一个确切原因的地方进行。这样，根据情况判断来看，原因指向了杀虫剂。在鱼很多的地方，鱼在鹰所吃的食物中占很大的比例(在阿拉斯加约占65%；在切沙皮克湾地区约占52%)。毫无疑问，由布罗勒先生长期研究的那些鹰绝大多数都是食鱼的。从1945年以来，这个特定的沿海地区一直遭受着溶于柴油的DDT的反复喷撒。这种空中喷药的主要目标是盐沼中的蚊子，这种蚊子生长在沼泽地和沿海地区，这些地方正是鹰猎食的典型地区。大量的鱼和蟹被杀死了。实验室从它们的组织里分析出含百万分之四十六高浓度的DDT。就像清水湖中的鸊鷉一样(鸊鷉由于吃湖里的鱼而使体内杀虫剂积累到很高浓度)，这些鹰当然也在它们体内组织中贮存了DDT。同样，如同那些鸊鷉一样，野鸡、鵪鹑和知更鸟也都越来越不能生育幼鸟来保持它们种类的繁衍了。 从全世界传来了关于鸟儿在我们现今世界中面临危险的共鸣。这些报告在细节上有所不同，但中心内容都是写继农药使用之后野生物死亡这一主题。例如，在法国用含砷的除草剂处理葡萄树残枝之后，几百只小鸟和鹧鸪死去了；或是在曾经一度以鸟类众多而闻名的比利时，由于对农场喷撒药而使鹧鸪遭了殃。 在英国，主要的问题看来有些特殊，它是和日益增长的在播种前用杀虫剂处理种子的做法相联系的。种子处理并不是新鲜事，但在早期，主要使用的药物是杀菌剂。一直没有发现对鸟儿有什么影响。然而到1956年，用一种双重目的的处理方法代替了老办法，杀菌剂、狄氏剂、艾氏剂或七氯都被加进来以对付土壤昆虫。于是情况变得糟糕了。 1960年春天，关于鸟类死亡的报告象洪水一样涌到了英国管理野生物的当局，其中包括英国鸟类联合公司、皇家鸟类保护学会和猎鸟协会。一位诺福克的农夫写道：“这个地方像一个战场，管理人员发现了无数的尸体，其中包括许多小鸟——鶸雀、绿莺雀、红雀、篱雀、还有家雀……野生生命的毁灭是十分可怜的。”一位猎场管理人写道：“我的松鸡已被用药处理过的谷物给消灭掉了，一种野鸡和其他鸟类，几百只鸟儿全被杀死了……对我这个终生的猎场看守人来说，这真是一件令人痛心的事情。看到许多对松鸡在一起死去是十分可悲的。” 在一份联合报告里，英国鸟类联合公司和皇家鸟类保护学会描述了67例鸟儿被害的情况——这一数字远远不是1960年春天死亡鸟儿的完全统计数。在此67例中，59例是由于吃了用药处理过的种子，8例由于毒药喷撒所致。 第二年出现了一个使用毒剂的新高潮。众议院接到报告说在诺福克一片地区中有600只鸟儿死去，并且在北易赛克斯一个农场中死了100只野鸡。很快就明显地看出了与1960年相比有更多的县郡已被卷进来了。(1960年是23郡，1961年是34郡。)以农业为主的林克兰舍郡看来受害最重，已报告有10，000只鸟儿死去。然而，从北部的安格斯到南部的康沃尔，从西部的安哥拉斯到东部的诺福克，毁灭的阴影席卷了整个英格兰农业区。 在1961年春天，对问题的关注已达到了这样一个高峰，竟使众议院的一个特别委员会开始对该问题进行调查，他们要求农夫、土地所有人、农业部代表以及各种与野生命有关的政府和非政府机构出庭作证。 一位目击者说：“鸽子突然从天上掉下来死去了。”另一位人报告说：“你可以在伦敦市外开车行驶一、二百英里而看不到一只茶隼。”自然保护局的官员们作证：“在本世纪或在我所知道的任何时期中从来没有发生过相类似的情况，这是发生在这个地区最大的一次对野生物和野鸟的危害。” 对这些死鸟进行化学分析的实验设备极为不足，在这片农村里仅有两个化学家能够进行这种分析(一位是政府的化学家，另一位在皇家鸟类保护学会工作)。目击者描述了焚烧鸟儿尸体的熊熊篝火的情景。然而仍努力地收集了鸟儿的尸体去进行检验，分析结果表明，除一只外，所有鸟儿都含有农药的残毒。(这唯一的例外是一只沙鹬鸟，这是一种不吃种子的鸟。) 可能由于间接吃了有毒的老鼠或鸟儿，狐狸也与鸟儿一起受到了影响。被兔子困扰的英国非常需要狐狸来捕食兔子。但是在1959年11月到1960年的4月期间，至少有1300只狐狸死了。在那些捕雀鹰、茶隼及其他被捕食的鸟儿实际上消失的县郡里，狐狸的死亡是最严重的，这种情况表明毒物是通过食物链传播的，毒物从吃种子的动物传到长毛和长羽的食肉动物体内。气息奄奄的狐狸在惊厥而死之前总是神智迷糊两眼半瞎地兜着圈子乱晃荡。其动作就是那种氯化烃杀虫剂中毒动物的样子。 所听到的这一切使该委员会确信这种对野生生命的威胁“非常严重”；因此它就奉告众议院要“农业部长和苏格兰州秘书应该采取措施保证立即禁止使用含有狄氏剂、艾氏剂、七氯或相当有毒的化学物质来处理种子。”该委员会同时也推荐了许多控制方法以保证化学药物在拿到市场出售之前都要经过充分的野外和实验室试验。值得强调的是，这是所有地方在杀虫剂研究上的一个很大的空白点。用普通实验动物——老鼠、狗、豚鼠所进行的生产性实验并不包括野生种类，一般不用鸟儿，也不用鱼；并且这些试验是在人为控制条件下进行的。当把这些试验结果应用在野外的野生物身上时决不是万无一失的。 英国决不是由于处理种子而出现鸟类保护问题的唯一国家。在我们美国这儿，在加利福尼亚及南方长水稻的区域，这个问题一直极为令人烦恼。多少年以来，加利福尼亚种植水稻的人们一直用DDT来处理种子，以对付那些有时损害稻秧的蝌蚪虾和羌螂甲虫。加利福尼亚的猎人们过去常为他们辉煌的猎绩而欢欣鼓舞，因为在稻田里常常集中着大量的水鸟和野鸡。但是在过去的十年中，关于鸟儿损失的报告，特别是关于野鸡、鸭子和燕八哥死亡的报告不断地从种植水稻的县郡那里传来。“野鸡病”已成了人人皆知的现象，根据一位观察家报道：“这种鸟儿到处找水喝，但它们变瘫痪了，并发现它们在水沟旁和稻田梗上颤抖着。”这种“鸟病”发生在稻田下种的春天。所使用的DDT浓度是已达到足以杀死成年野鸡量的许多倍。 几年过去了，更毒的杀虫剂发明出来了，它们更加重了由于处理种子所造成的灾害。艾氏剂对野鸡来说其毒性相当于DDT的l00倍，现在它已被广泛地用于拌种。在得克萨斯州东部水稻种植地区，这种做法已严重减少了褐黄色的树鸭、(一种沿墨西哥湾海岸分布的茶色、象鹅一样的野鸭)的数量。确实，有理由认为，那些已使燕八哥数量减少的水稻种植者们现在正使用杀虫剂去努力毁灭那些生活在产稻地区的一些鸟类。 “扑灭”那些可能使我们感到烦恼或不中意的生物的杀戒一开，鸟儿们就愈来愈多地发现它们已不再是毒剂的附带被害者而成为毒剂的直接杀害目标了。在空中喷撒象对硫磷这样致死性毒物的趋势在日益增长，其目的是为了“控制”农夫不喜欢的鸟儿的集中。鱼类和野生物服务处已感到它有必要对这一趋势表示严重的关注，它指出“用以进行区域处理的对硫磷已对人类、家畜和野生物构成了致命的危害。”例如，在印第安州南部，一群农夫在1959年夏天一同去聘请一架喷药飞机来河岸地区喷撒对硫磷。这一地区是在庄稼地附近觅食的几千只燕八哥的如意栖息地。这个问题本来是可以通过稍微改变一下农田操作就能轻易解决的——只要改换一种芒长的麦种使鸟儿不再能接近它们就可以了，但是那些农夫们却始终相信毒物的杀伤本领，所以他们让那些撒药飞机来执行使鸟儿死亡的使命。 其结果可能使这些农夫们心满意足了，因为在死亡清单上已包括有约65，000只红翅八哥和燕八哥。至于其他那些未注意到的、未报道的野生物死亡情况如何，就无人知晓了。对硫磷不只是对燕八哥才有效，它是一种普遍的毒药，那些可能来到这个河岸地区漫游的野兔、浣熊或袋鼠，也许它们根本就没有侵害这些农夫的庄稼地，但它们却被法官和陪审委员团判处了死刑，这些法官们既不知道这些动物的存在。也不关心它们死活。 而人类又怎么样呢？在加利福尼亚喷撒了这种对硫磷的果园里，与一个月前喷过药的叶丛接触的工人们病倒了，并且病情严重，只是由于精心的医护，他们才得以死里逃生。印第安州是否也有一些喜欢穿过森林和田野进行漫游、甚至到河滨去探险的孩子们呢？如果有，那么有谁在守护着这些有毒的区域来制止那些为了寻找纯洁的大自然而可能误入的孩子们呢？有谁在警惕地守望着以告诉那些无辜的游人们他们打算进入的这些田地都是致命的呢？——这些田地里的蔬菜都已蒙上了一层致死的药膜。然而，没有任何人来干涉这些农夫，他们冒着如此令人担心的危险，发动了一场对付燕八哥的不必要的战争。 在所有这些情况中，人们都迴避了去认真考虑这样一个问题：是谁作了这个决定，它使得这些致毒的连锁反应运动起来，就象将一块石子投进了平静的水塘，这个决定使不断扩大的死亡的波纹扩散开去？是谁在天平的一个盘中放了一些可能被某些甲虫吃掉的树叶，而在天平的另一个盘中放入的是可怜的成堆杂色羽毛——在杀虫毒剂无选择的大棒下牺牲的鸟儿的无生命遗物？是谁对千百万不曾与之商量过的人民作出决定——是谁有权力作出决定，认为一个无昆虫的世界是至高无上的，甚至尽管这样一个世界由于飞鸟搭拉的翅膀而变得暗然无光？这个决定是一个被暂时委以权力的独裁主义者的决定；他是在对千百万人的忽视中作出这一决定的，对这千面万人来说，大自然的美丽和秩序仍然还具有一种意义，这种意义是深刻的和必不可少的。