Lost Woods (4 page)

Some 2,000 years ago Aristotle declared that eels were generated spontaneously from mud. Even today there are people who still subscribe to the ancient belief that a horse hair falling into water becomes an eel. Within the past two decades, reputable scientists knew little more than the fact that spring and fall the eels are running in the rivers – in the fall the old eels are bound for the sea, in the spring the young are ascending every bay and river estuary.

Four and a quarter centuries after the Nina, the Pinta and the Santa Maria crossed the dread sea of floating sargassum weed another explorer, Danish Johannes Schmidt, sailed over a spot in the Sargasso, south of Bermuda and a thousand miles east of Florida, and declared it to be the breeding place of the eel. In twenty years of painstaking research he had literally strained the surface waters of the ocean for eel larvae, finding younger and younger stages all the way across the Atlantic from Europe, until at last he found the youngest stage of all and knew he had reached the birthplace of the eels.

Let’s picture the spawning journey of a Chesapeake Bay eel. Part of it we know from observed fact; part we shall have to supply from imagination aided by our knowledge of later happenings. If our eel lives far up toward the headwaters of one of the rivers tributary to the bay, it is almost certain to be a female, for the males usually remain in salty or brackish water near the river mouths.

Other autumns to the number of ten, fifteen or twenty have come and gone, but our eel has never before felt the desire to leave the familiar mud banks dotted with crayfish burrows, the marshy banks where small fowl or water rats could now and then be seized, the forests of water weeds where hunting was good for minnows, sunfish, and perch.

Now physical maturity has attuned her to the call of seaward hurrying water. One dark night, when wind ruffles the surface of the river and clouds hide the moon, she slips away downstream on the journey which she will never retrace. Hiding by day, drifting with the currents by night, she finds the river ever widening, the channels deepening, the water bringing unfamiliar tastes to her keen senses.

She is not alone; more and more eels have joined the caravan. Probably as their numbers increase and the strange, bitter tang of salt grows stronger in the water the excitement of the eels grows, they travel faster, rest less often. In the lower estuary of the river the male eels have been living, growing fat on shellfish, worms and water plants – on shad and herring looted from fishermen’s gill nets in the spring. Compared with the 3- to 4-foot females, however, the males are dwarfs, never growing to a greater length than two feet.

Gradually the river garb of olive brown is changed for a coat of glistening black with under parts of silver: This is the dress worn only by eels about to undertake the far journey to the Sargasso. The snouts become high and compressed, probably owing to some sharpening of the sense of smell; the eyes become twice their former size, as though in preparation for the descent along darkening sea lanes.

After the eels leave our shores nothing more is seen of them. The only clue to their destination is the finding of the newly hatched larvae floating nearly a thousand feet below the surface of the Sargasso Sea. How do the migrants find their way? Perhaps one man’s guess is as good as another. The English naturalist Henry Williamson suggests the eels find the Gulf Stream and swim against its current, their keen nostrils scenting in its warm waters the rotting sargassum weed.
*

Even more puzzling, how do the fragile larvae, as transparent as glass and flattened like a willow leaf, find their way back to the shores from which the parents came? And how do the children of the American and European eels return to the proper continent?

When a few months old and less than an inch long, eel larvae begin their homeward migration, aided by the movements of the water currents. Since the breeding grounds of the European and American eels overlap, the larvae of the two species travel together for a time. (The European eel has a larger number of vertebrae and so may be distinguished even as a larva.) Finally, the two great stream of larvae begin to diverge, the American eels turning westward, the European eastward.

From January to March, when something less than a year old, American eel babies are arriving in coastal waters off the Chesapeake, off New England somewhat later. At that time European eel babies are somewhere in mid-Atlantic and will not reach shore until they are 3 years old.

As a partial explanation of the infallible homing instinct of the two species of eels, scientists point out that the American eel undergoes a change from the flat, leaflike larva to the rounded “glass-eel” stage when it is only a year old, while the European eel requires two years more. Until this stage is reached, scientists say, the young eels feel no urge to seek the coast – therefore there is no chance that a young European eel will make port in the wrong continent.

When the young eels begin to enter our rivers they are from 2 to 3½ inches long and practically colorless except for the eyes. The segregation of the sexes is already apparent, the males remaining in tidal marshes and brackish river mouths, the females pushing upstream, clambering over falls, up dams, even over damp rocks. “Elvers,” as they are called, swim at or near the surface, often forming an unbroken procession extending for miles along the edges of rivers or creeks.

In some European rivers the elvers themselves are taken for food; in others they are caught for stocking in other rivers less plentifully supplied with eels for the ready European markets.

Although not in great favor in local markets, eels support one of the more important Chesapeake fisheries. Out of the thirty-six varieties of fishes produced in Maryland waters, eels rank ninth in poundage, eighth in value. About a quarter of a million pounds are produced in Maryland, this figure being a little more than half of the total Chesapeake yield. Most of the output is shipped to New York and other distant markets, but part of the catch is consumed locally and part is used as bait, especially on trotlines fished for hard crabs. The Maryland Legislature once (about 1890) spent $3,400 in an attempt to exterminate eels because of their frequent raids on fishes caught in gill nets.

4

[1944]

Ace of Nature’s Aviators

IT WAS TYPICAL
of Rachel Carson’s literary craftsmanship and scientific understanding that she could find in the most mundane parts of the natural world some aspect that endowed the familiar with a unique sense of worth, even redemptive value. An early example was a feature article rehabilitating the common starling which first appeared in the Baltimore
Sun
in early 1939. Carson sold a revised version to
Nature Magazine
later that same year as “How About Citizenship Papers for the Starling?” It brought favorable comment from readers who were fascinated to learn something of the worthiness of this much maligned bird.

Research that came across Carson’s Fish and Wildlife desk during the war years reinforced her determination to write about scientific topics that would inform the public as well as make the hidden processes of nature understandable to the general reader. “Ace of Nature’s Aviators” reports the discovery of the remarkable migration patterns of the “remote and mysterious” chimney swift. It began as a Department of Interior press release. Having revised it as a feature article, Carson offered it to the Baltimore
Sun
and to
Reader’s Digest,
but since she was in need of immediate money following an appendectomy, she hastily sold a condensed version to
Coronet
which was published as “Sky Dwellers” in November, 1945.

IF AVIATION ENGINEERS
could apply the wisdom of the chimney swift, several troublesome problems of aeronautics could be solved. Pilots, for example, would never have to worry about the amount of gasoline in their tanks. The chimney swift refuels on the wing, spends almost its entire waking life in the air, and never, except by accident, touches the earth.

In creating one of her most efficient mechanisms for flight, Nature has fashioned the swift as a flying insect trap. Its beak is short, its mouth one of the widest in birddom. Its torpedo-shaped body and long, slender wings are built for speed and adapted to sudden twists and turns. From dawn till dusk the swift speeds open mouthed through the sky, straining insects out of the air. Although the bird’s aerial existence involves a high rate of fuel consumption, its energy is perpetually renewed by the almost continuous intake of food.

Not only does it eat in the air, the chimney swift drinks and bathes on the wing, dipping to the surface of a pond for a momentary contact with the water; its courtship is aerial; it sometimes even dies in the sky. Probably it is less aware of the earth and its creatures than any other bird in the world. It never perches on a tree, never alights on the ground. Its whole existence is divided between the sky and a nocturnal resting place inside a chimney or a hollow tree.

For its mastery of the air, the swift has paid a strange penalty. Its feet have degenerated into little more than hooks, useless for perching or hopping as other birds do, but perfect for clinging to the wall of a chimney. As a result of its inability to perch, the swift’s idea of going to bed is merely to hang itself up for the night against some vertical surface, its toes securely hooked in a crack or over a convenient projection. Its stubby tail, edged with a row of bristles, provides a useful prop.

The chimney swift is one of the few birds unharmed by the white man’s invasion of North America – it has actually profited by it. Ancestors of the modern chimney swift lived in great hollow trees. When pioneering Americans began to cut down the forests and to build cabins and houses, then churches, schools, and factories, the swifts discovered that a chimney is a first-rate substitute for a hollow tree. Almost to a bird they changed their habits.

In more isolated parts of the country, a few chimney swifts cling to old-fashioned ideas: they still nest in hollow trees. The western cousin of the chimney swift – Vaux’s swift – only of recent years has begun to make the transition from trees to chimneys. So broadminded and so adaptable is the true chimney swift, however, that it has made the most of various other conveniences of civilization, nesting in abandoned buildings, in wells and cisterns, and in silos.

For its intra-chimney architecture the swift is equipped with enormously developed salivary glands. These secrete a thick, gluey saliva useful in fastening twigs together and in cementing the hammocklike nest to the wall of the chimney. The Chinese swift dispenses with twigs, fashions its entire nest of saliva, and so creates the principal ingredient of the delicacy known as bird’s nest soup.

During the nesting season the salivary glands enlarge, providing copious supplies of the needed cement. Later they shrink, but the hollow spaces left in the cheeks of the swift are put to good use – the bird crams them full of insects to bring back to its hungry babies.

Nest building takes two to three weeks, even longer if the days are rainy and the glue melts. Every twig used is collected by an amazing method: the bird snatches them on the wing from trees and shrubbery. To this day ornithologists cannot agree whether it uses feet or beak in the process.

Swifts are devoted parents. The male and female take turns incubating the eggs during the nearly three weeks required for the young to hatch. Thereafter, both birds assume the chore of keeping the infant mouths filled with insects, a task that must be performed faithfully for about four weeks before the young swifts are able to take to the sky in their own behalf.

Unexplained as yet is the fact that observers have sometimes seen three adult birds tending a nest. The polite but wholly tentative theory is that the parents have engaged a “nursemaid.” More realistic persons scoff at that and say the swift is polygamous. What the truth is, no one actually knows.

The chimney swift is rated the fastest small bird in North America and has few natural enemies it needs to fear. Flight records for an Asiatic swift indicate speeds up to 200 miles an hour. It is debatable whether even a duck hawk can overtake one in straight-away flight. An occasional swift, however, may be snatched by a hawk as the birds are circling above a chimney, preparatory to entering for the night.

From one enemy – rain – the bird has no defense. Cold rains, long continued, wash the skies clear of insects. Deprived of food, the swifts weaken and die in great numbers. During one unseasonably wet June reports of dead swifts came from all over southern New England, wheelbarrow loads were taken from the chimneys of large mills, bushels from the base of a chimney at Clark University. Fortunately, such occurrences are comparatively rare.

The life story of the chimney swift has been pieced together by naturalists and amateur birders only with the greatest patience and perseverance. A bird who never perches on a tree where you can focus your binoculars on him, who never visits feeding stations, who spends almost all the daylight hours far above your head, and who, in the fall, vanishes so suddenly and completely that only within the past year has his winter home been discovered – such a bird is not an easy subject for his would-be biographers.

Perhaps because of the very difficulty of the job, an extraordinary number of people seem to have interested themselves in the chimney swift, and have gone to endless trouble to learn its habits. One woman in Iowa had an imitation chimney, equipped with observation tower, built in her back yard so she could study the home life of the swifts that later nested in it. A West Virginia farmer suspended tin coffee cans in his chimney as an invitation to the swifts to nest there. The birds accepted, later permitted the farmer to raise the cans to the top of the chimney at intervals to photograph the young. The ornithologist and artist George Mitsch Sutton, as a young man in West Virginia, repeatedly climbed a tall church chimney and hung for hours, cramped, shivering, and wretched, just below the mouth of the chimney so he could make accurate notes on the wing movements of the swifts as they dropped into the chimney. And all over eastern United States and Canada, people have industriously banded chimney swifts in an effort to trace their migrations, until the total of swifts marked with identifying metal bands now exceeds 375,000.

Banding 375,000 chimney swifts is not as simple as it may seem. If you are one who insists upon lying abed in the chilly dawn or whose experience as a steeple jack is limited, don’t take up swift banding as a hobby. It requires a certain Spartan fortitude. Unlike most birds, the insect-eating swifts cannot be attracted to cage traps baited with grain or other foods. They have to be caught as they emerge at daybreak from the large chimneys where thousands of them sleep, especially near the time of the fall migration.

Swift banders stand about on roofs, shivering as they wait for daylight and the birds. They risk their necks clambering to the tops of tall chimneys to set their traps. They incur the suspicion of the law as they skulk about empty buildings in the small hours. Despite these hazards, Constance and E. A. Everett of Minnesota once wrote cheerfully to an ornithological journal about “the fun of banding chimney swifts.”

A few months ago the banders had their reward. Although many marked swifts had been recaptured, all recoveries had been made within the known summer range of the bird, and the winter home of the swift was still undiscovered. Then to the U.S. headquarters for the study of bird migration, the Fish and Wildlife Service, came a long, official envelope from the American Embassy at Lima, Peru. It contained thirteen bands, taken from chimney swifts shot by Indians in the jungles of Peru during the northern winter. Records showed that the birds had been banded in Tennessee, Illinois, Connecticut, Alabama, Georgia, and Ontario, dates of banding ranging from 1936 to 1940.

For the thirteen small birds, death won ornithological fame. The swift was the last North American bird whose winter range was unknown. The thirteen had now provided the solution of a major mystery of bird migration, had filled in the missing paragraphs in the biography of their race.