Being able to fly didn't help

Century After Extinction, Passenger Pigeons Remain Iconic—And Scientists Hope to Bring Them Back

I heard someone talking on Radio National about this last week:  the remarkable extinction of a North American pigeon breed which numbered in the billions, and was (reliably) said to darken the skies for at least hours, if not days, during its migrations.

Here's a description from another article:

In May 1850, a 20-year-old Potawatomi tribal leader
named Simon Pokagon was camping at the headwaters of Michigan's Manistee
River during trapping season when a far-off gurgling sound startled
him. It seemed as if "an army of horses laden with sleigh bells was
advancing through the deep forests towards me," he later wrote. "As I
listened more intently, I concluded that instead of the tramping of
horses it was distant thunder; and yet the morning was clear, calm, and
beautiful." The mysterious sound came "nearer and nearer," until Pokagon
deduced its source: "While I gazed in wonder and astonishment, I beheld
moving toward me in an unbroken front millions of pigeons, the first I
had seen that season."

These were passenger pigeons, Ectopistes migratorius, at the
time the most abundant bird in North America and possibly the world.
Throughout the 19th century, witnesses had described similar sightings
of pigeon migrations: how they took hours to pass over a single spot,
darkening the firmament and rendering normal conversation inaudible.
Pokagon remembered how sometimes a traveling flock, arriving at a deep
valley, would "pour its living mass" hundreds of feet into a downward
plunge. "I have stood by the grandest waterfall of America," he wrote,
"yet never have my astonishment, wonder, and admiration been so stirred
as when I have witnessed these birds drop from their course like meteors
from heaven."...

In forest and city alike, an arriving flock was a spectacle--"a
feathered tempest," in the words of conservationist Aldo Leopold. One
1855 account from Columbus, Ohio, described a "growing cloud" that
blotted out the sun as it advanced toward the city. "Children screamed
and ran for home," it said. "Women gathered their long skirts and
hurried for the shelter of stores. Horses bolted. A few people mumbled
frightened words about the approach of the millennium, and several
dropped on their knees and prayed." When the flock had passed over, two
hours later, "the town looked ghostly in the now-bright sunlight that
illuminated a world plated with pigeon ejecta."

 Update:  from another article, talking about the ease of getting dinner when a gigantic flock was overhead:

These flocks were so densely packed that a single shot could bring down 30-40 birds. He birds could be brought down and killed just by hitting them with pieces of wood as they flew over hilltops. The bird's only natural predators were hawks and eagles. As they flew, they covered settlements with droppings, once an important way of spreading seeds, but viewed as a nuisance by settlers.

 The massive, industrial scale over-hunting for food and fun in the 1800's is also described:

After 1830 the pigeons were hunted for sport, hog feed and even for agricultural fertiliser. In the 1870s, 250,000 Passenger pigeons a year were released from live traps for shooting practice. Its decline began in earnest with the onset of large-scale commercial hunting carried out by well-organised trappers and shippers supplying cheap meat to the developing cities on the east coast of the USA. The opening of railroads linking the Great Lakes area with New York meant 300,000 Passenger pigeons were sent to New York during 1855 alone. The most devastating killings were during the 1800s and 1870s. Th figures were recorded as a normal part of commerce: 23rd July, 1860 (23 July) saw 235,200 birds sent east from Grand Rapids in Michigan; 1874 saw 1,000,000 birds shipped east from Oceana County in Michigan; 1876 saw 1,600,000 shipped east from Oceana County (400,000 per week during the season). In 1869, Van Buren County, Michigan, shipped 7,500,000 birds to the east. In 1880, 527,000 birds were shipped east from Michigan.

 I'm surprised I hadn't heard the details of this extraordinary animal and its extinction before...