Ectopistes migratorius

Artifact of nostalgia: Lewis Lumen Cross's Bird's Eye View of Passenger Pigeons Nesting (1937)

In 1600, billions of passenger pigeons populated the forests of North America east of the Rockies to the Atlantic Coast, from southern Canada to the Gulf of Mexico as they had for 100,000 years.  Today, there are none. What happened to them?

Until the mid 1800's at certain times of the year depending on where you lived, the sky would be black with them for hours as they followed the growing cycle in search of food, traveling in bands a mile wide and mile after mile after mile in length. But by 1857, the dwindling number was apparent enough that the Ohio legislature considered enacting a law to protect them.  That recognition notwithstanding, on September 1, 1914 the last known passenger pigeon, a female named Martha -- the sole survivor of a last ditch breeding effort-- died in the Cincinnati Zoo. Her preserved body is in the Smithsonian archives.

Without the pressure of habitat-consuming humans, passenger pigeons had evolved a survival advantage over predators in their sheer number.  Living in vast swarms was not merely a convenience but a necessity, and as such, one that worked against any prospects of domestication.  But from a food perspective, domestication of passenger pigeons was not a priority for humans since for millennia, the sheer number of pigeons in the wild provided a plentiful seasonal food source even before the arrival of Europeans.  The first Europeans discovered the trade-off of a noisy flock of pests who without mitigation ravaged crops yet provided protein in abundance.  But the pestilence worked in reverse as well. As Europeans replaced First Nation peoples in their expansion west, they replaced the woodland habitat of the passenger pigeon with farms, towns, cities, roads and railroads, posing one of the first major threats to passenger pigeon survival.  As they were already a staple of the early American diet, fewer passenger pigeons in the settled East contributed to the success of a market for squab, the preferred meat of birds too young to have reproduced.  To keep the East well stocked with squab, hunters employed tricks established in Europe which worked devastatingly on passenger pigeon populations.  

Shoshana Zuboff* describes it:

... Bernd Heinrich describes the fate of the passenger pigeons, whose “social sense was so strong that it drew the new predator, technologically equipped humans, from afar. It made them not only easy targets, but easily duped.” Commercial harvesters followed the pigeons’ flight and nesting patterns, and then used huge nets to catch thousands of pigeons at a time, shipping millions by rail each year to the markets from St. Louis to Boston. The harvesters used a specific technique, designed to exploit the extraordinary bonds of empathy among the birds and immortalized in the term “stool pigeon.” A few birds would be captured first and attached to a perch with their eyes sewn shut. As these birds fluttered in panic, the flock would descend to “attend to them.” This made it easy for the harvesters to “catch and slaughter” thousands at once. 

The effect of habitat destruction and mass slaughter of birds for food and for sport had an observable effect on the population to such a degree that in 1857

a bill was brought forth to the Ohio State Legislature seeking protection for the Passenger Pigeon. A Select Committee of the Senate filed a report stating, "The passenger pigeon needs no protection. Wonderfully prolific, having the vast forests of the North as its breeding grounds, traveling hundreds of miles in search of food, it is here today and elsewhere tomorrow, and no ordinary destruction can lessen them, or be missed from the myriads that are yearly produced." 

As is often the case where politics substitutes for science, the conclusion of the committee was soon to be proven wrong.  In 1897, with the population almost depleted, Michigan, at the heart of the passenger pigeon's territory, enacted a poorly enforced 10-year moratorium on hunting within 2 miles of the species' nesting areas.  But it was too little too late.  A University of Chicago ornithologist Charles Otis working in conjunction with the Cincinnati Zoo in the early 1900s was the last to attempt reviving the species with the offspring from only 2 birds, but with the population down to 12, they stopped breeding altogether, and just aged and died one by one until only Martha was left.  

According to a 2017 study published in Science, the depletion of the passenger pigeon population  was so rapid that that there was no time for the species to adapt to the dramatic shift in population density.  In effect, so engrained in passenger pigeon DNA was the certainty of numerousness that the human destruction of that essential of passenger pigeon survival began a negative feedback loop resulting in a downward spiral of the species' population that, barring a miraculous adaptation, could only result in extinction.

As Bernd Heinrich (quoted in Zuboff) writes:

The pigeon had no home boundaries over which to spread itself and continued to orient only to itself, so it could be everywhere, even to the end.… To the pigeons, the only ‘home’ they knew was in the crowd, and now they had become victims of it… the lack of territorial boundaries of human predators had tipped the scales to make their adaptation their doom.

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* The quote is from Shoshana Zuboff's The Age of Surveillance Capitalism.  Zuboff is making an analogy between the hunting strategy and the way in which likes on social media tend to beget likes, creating an atmosphere in which particularly young users seek and are granted or denied valorization via the extent of their popularity on social platforms so that their data and habits can be monetized by those very platforms.