It was cool, 55 degrees, that day 100 years ago on farmland near
Sargents, in southern Ohio's Pike County.

      Press Clay Southworth was just 14 years old when he persuaded his
mother to let him take the 12-gauge shotgun and shoot the bird that was
eating the corn on the family farm.

      "I found the bird perched high in the tree and brought it down
without much damage to its appearance," Press Southworth would write 68 years later at the age of 82. "When I took it to the house Mother
exclaimed - "It's a passenger pigeon!'"

      Young Press Southworth shot this passenger pigeon on March 24,
1900, but it would take more than decade for anyone to determine that
Mr. Southworth's quarry that day was the last passenger pigeon ever
recorded from the wild.

        The Southworth passenger pigeon survives today as a specimen at
the Ohio Historical Society in Columbus; it is called Buttons, because the
woman who prepared the specimen used black shoe buttons for its eyes.

        The Ohio Historical Society is using the occasion of the 100 th
anniversary today to raise the awareness of visitors and school children to
the spectre of extinction, calling the anniversary an "unfortunate
milestone in history."

        And just 14 years later, on Sept. 1, 1914, the last passenger pigeon
in the world died in captivity at the Cincinnati Zoo. Martha was discovered lying on the bottom of her cage at 1 p.m.

        Environmentalists and conservation groups all point to the
passenger pigeon and its extinction as a benchmark, as a lesson in the
perils of arrogance.

        Dr. David Olson, a conservation biologist with the World Wildlife
Fund in Washington D.C., says the passenger pigeon was a warning to
conservationists about how quickly extinction can occur, especially when
hastened by the hand of man.

        "Passenger pigeons are a real red flag for us," said Dr. Olson.
"Their precipitous decline is really alarming. It went in just a few years
from literally millions to almost none."

        Passenger pigeons were a super-abundant bird, perhaps the most
populous bird ever to inhabit the planet and certainly North America, A.W. Schorger, in his definitive book on the life history of passenger pigeons (The Passenger Pigeon: Its Natural History and Extinction, 1955), estimates its population at 3 to 5 billion birds before they declined.

        Naturalists and artists waxed poetic on the migratory events of
passenger pigeons overhead. They darkened the skies, blotting out the
sun; they were swift, their flight reaching speeds of 60 mph; and their
passing sounded like thunder. John James Audubon

        wrote of traveling in Kentucky in 1813 and watching a flock pass
overhead for three full days.

        State legislatures saw no need to protect the species. It seemed
akin to protecting ants. A committee of the Ohio Legislature in 1857 was
fairly typical when it asserted, "The passenger pigeon needs no
protection."

        So what happened?

        The birds were slaughtered. They were killed for food, for their
feathers, for sport. Forests began disappearing, which the vast numbers
depended on for mast - beechnuts and acorns, among other nuts and
berries. When their numbers dwindled, the species passed a threshold
from which it could not recover.

        It happened quickly. By the 1870s and '80s, they were becoming
scarce, sightings infrequent. It was a species that needed abundance to
survive, from its feeding forays to its colonial nesting behavior. Without
vast numbers, it slipped below a sustainable threshold.

        "Passenger pigeons are a great example of where they reached that
threshold and they just kept going," said Dr. Olson.

        But it is the passenger pigeon's legacy that endures as a
conservation ethic.

        Robert Glotzhober, curator of natural history at the Ohio Historical Society, said the lesson posited 100 years ago is that we are tipping the balance towards extinction.

        "There's a concern there," said Mr. Glotzhober. "What will our world be as times goes by and we have more extinctions and fewer species? Ecologists suggest that the more you simplify systems of living organisms the less stable they become. That means you're more likely to have massive die-offs, starvations, loss of additional species, increase of
pests, all kinds of things. So the greater the diversity, usually the more
stable. To sustain human life that's what we want, a stable system."

        Scientists need to get a handle on where those thresholds exist,
what they might be and what can be done to prevent them from being
crossed, said Dr. Olson.

        "The broader implication is that there are many other species that
are seemingly abundant but may be just as fragile below a certain point,"
said Dr. Olson. "They can quickly decline despite protection and
apparently abundant habitat. Neotropical migrant songbirds are a good
example."

        Before the turn of the century it became apparent that passenger
pigeons were far and few between. By the turn of the century, there were
no sightings. Rewards were offered. By 1910, a standing reward of
$1,000, made by individuals, was offered for information leading to a
nesting pair or colony. The Cincinnati Zoo was offering a $1,000 reward for a male passenger pigeon that would mate with its female pigeon, Martha. The rewards were never claimed.

        While the passenger pigeon could not be saved, the zoo did save
one of its aviaries in 1974. It was where Martha lived.

        Built in 1875, the aviary was moved, remodeled and turned into a
Passenger Pigeon Memorial. While three mounted specimens and one
skin are on display in the memorial, Martha herself is not.

        Martha had been promised to the Smithsonian Institution when she
died; she was packed in a 300-pound block of ice and shipped to
Washington D.C., where she is on display at the Smithsonian's Museum
of Natural History.

        Dave Oehler, head of the zoo's aviculture department, said the
memorial, located across from the Cat House, is a place for reflection.

        "The building itself is very quiet," said Mr. Oehler. "It's not only a sobering experience, but you can spend some time in there and reflect on
what happened. It's a nice, quiet little place to come. Then you can go
back out and enjoy the wildlife."