Two hundred years ago, the passenger pigeon was one of
 North America's greatest natural wonders, the equivalent
 of Niagara Falls or the Grand Canyon. A hundred years later
 it was gone, as lost as the dinosaurs. In "A Feathered River
 Across the Sky," Joel Greenberg, a research associate at
 Chicago's Field Museum, tells the achingly sad story of
how this singular species, once the most numerous bird
on the planet, went extinct.

A Feathered River Across the Sky

By Joel Greenberg
Bloomsbury, 289 pages, $26

The passengepigeon—a relative of the common 
city pigeon but larger and more brightly colored, with a
 long tail—once flew in America's skies in flocks of
 astonishing size. Around 1860, an English naturalist
 visiting America wrote that "early in the morning . . .
I was perfectly amazed to behold the air filled, the sun
obscured by millions of pigeons . . . in a vast mass a
mile or more in breadth, and stretching before and
 behind as far as the eye could reach. . . . It was late
 afternoon before any decrease in the mass was
 perceptible, . . . the column (allowing a probable
velocity of sixty miles an hour) could not have been
 less than three hundred miles in length." That suggests
 there were more than 3.7 billion birds in that flock—
only a portion of the entire continental population. This
 report wasn't an outlier. Such distinguished ornithologists
 as Alexander Wilson and John James Audubon reported
 similar sightings, as did many others.

But on Sept. 1, 1914, Martha, a denizen of the Cincinnati
 Zoo, was found dead in her cage. She was the last of her
kind. Stuffed and mounted, she is in the Smithsonian,
although not currently on display. What could have
driven a bird so abundant as to blot out the sun itself
into extinction in only half a century? As Mr. Greenberg
makes clear, it was the combination of three factors:
the species' peculiar nesting habits, the Industrial
Revolution and human ignorance.
The passenger pigeon was a child of the once vast
eastern North American forest, a forest that stretched
 unbroken from the Atlantic to well past the Mississippi.
The nut trees of this forest, such as oak and beech,
 produced mast in prodigious quantities, which animals
 like the passenger pigeon would feed on. But mast is
 produced irregularly. One year, in one area, there is a
 bumper crop; the next year that area will likely produce
 next to none.
So passenger pigeons not only migrated in vast numbers;
they also nested that way, flocking to an area where lots
 of mast had been produced the previous fall. These
nesting areas could themselves be almost unimaginably
 huge: One in Wisconsin in 1872 covered a staggering
850 square miles of forest. A single tree might contain a
 hundred nesting pairs or more. Some observers reported
 trees with as many as 600 nests.
In the morning, the males would leave the nesting area to
 forage, returning at midday, when the females would leave.
 About two weeks after the eggs hatched, the adults
abandoned the well-fed, indeed roly-poly, squabs, who
 would flutter down to the ground and begin feeding for
 themselves. After a few days they would be strong
enough to fly away.
Mass nestings in unpredictable locations were an effective
reproductive strategy for the passenger pigeon as a species.
 Predators who happened to be nearby would have a field
 day, but with so many pigeons and squabs, they could
hardly make a dent in the total numbers. Even in the early
days of European settlement, when settlers armed with
 shotguns discovered they could bring down a dozen or
 more pigeons with a single blast, human hunters weren't
numerous enough to be a threat to the birds.
But in the 19th century the burgeoning population of the
 United States surged westward, and the forest was
increasingly turned to farmland. The big eastern cities,
 growing in size, needed cheap food, and nothing was
more plentiful and cheap than pigeon, which could be
 cooked like chicken, then a semi-luxury dish. But it was
the railroad and the telegraph, which began to spread
across the landscape in the 1830s and '40s, that proved
 lethal to the species.

Previously, hunters' inability to predict where passenger
 pigeons would nest in a given year protected the creatures.
With the telegraph, however, the news of a major nesting
 could move at the speed of light. With the railroad, market
 hunters could converge in a few days and then send the
slaughtered pigeons to market.
And slaughtered they were. Mr. Greenberg quotes one
 pigeoner at the great Wisconsin nesting of 1872 attacking t
he departing males in the morning. "Hundreds, yes thousands,
 dropped into the open fields below. . . . The slaughter was
 terrible beyond any description. Our guns became so hot
 by rapid discharges we were afraid to load them. . . . Below
 the scene was truly pitiable. Not less than 2,500 birds
covered the ground."
Having killed as many of the males as they could, the hunters
moved in on the females and the squabs, who, unable to fly
yet, were easy pickings. Mr. Greenberg reports one estimate
 that at least a hundred barrels, each holding 300 birds, were
 shipped daily during the 40 days that the hunt lasted. That
 doesn't count the birds that were shipped alive, consumed
 locally, or just left to rot. Nor does it count the myriad squabs
 who starved to death in the nests because their parents had
 been killed.
Besides guns, nets were used. Designed like vast mouse
 traps, they would be baited with corn and other grains and
 with tame birds to lure the wild ones (this was the origin of
the term "stool pigeon," because the birds were tethered to
 a small platform called a stool). When enough birds had
gathered, the trap would be sprung and snap over the victims.
The catch could be enormous. One spring of a trap in
Wisconsin yielded 35,000 birds. A three-man team in 1878
netted more than 50,000 birds during the hunting season.
With this sort of predation, the number of passenger pigeons
 declined rapidly. As it did so, the market hunters converged
 on the remaining flocks, and the population crashed. By the
1890s the flocks were too scattered and few to be worth
pursuing anymore.
By that time it was too late. The last definite specimen to be
 shot in the wild died in 1898. The last birds seen in the wild
 were observed about a decade later. No less a bird-watcher
than Theodore Roosevelt wrote to friends about seeing a flock
of seven on May 18, 1907, in Albemarle County, Virginia. But
 there is enough of a note of doubt in his report to make one
 wonder if this was a case of "faith-based observation." By
1912, only a few birds, all captive, remained.
Joel Greenberg has done prodigious research into the
 literature of the passenger pigeon and lays much of it out
 in this book. For that effort, all who care about the living
 world owe him a debt of gratitude. But he fails to make a
dramatic narrative of this dramatic tale, instead simply
 retelling one anecdote after another. "A Feathered River
 Across the Sky," however, does make you understand
 the pathos of the great ornithologist William Beebe when
 he wrote, in 1906, that "when the last individual of a race
 of living beings breathes no more, another heaven and
 another earth must pass before such a one can be again."
—Mr. Gordon is the author of "Hamilton's Blessing:
The Extraordinary Life and Times of Our National Debt."