|Common Name||Wild Pigeon|
The Passenger Pigeon or wild pigeon, (Ectopistes migratorius), is an extinct North American bird. The species lived in enormous migratory flocks until the early 20th century, when hunting and habitat destruction led to its demise. One flock in 1866 in southern Ontario was described as being 1 mi (1.5 km) wide and 300 mi (500 km) long, took 14 hours to pass, and held in excess of 3.5 billion birds. That number, if accurate, would likely represent a large fraction of the entire population at the time.
Some estimate 3 to 5 billion Passenger Pigeons were in the United States when Europeans arrived in North America. Others argue the species had not been common in the pre-Columbian period, but their numbers grew when devastation of the American Indian population by European diseases led to reduced competition for food.
The species went from being one of the most abundant birds in the world during the 19th century to extinction early in the 20th century. At the time, Passenger Pigeons had one of the largest groups or flocks of any animal, second only to the Rocky Mountain locust.
Some reduction in numbers occurred from habitat loss when European settlement led to mass deforestation. Next, pigeon meat was commercialized as a cheap food for slaves and the poor in the 19th century, resulting in hunting on a massive and mechanized scale. A slow decline between about 1800 and 1870 was followed by a catastrophic decline between 1870 and 1890. Martha, thought to be the world's last Passenger Pigeon, died on September 1, 1914, at the Cincinnati Zoo.
Ecology and Behavior
The Passenger Pigeon was one of the most social land birds. It lived in colonies stretching over hundreds of square miles and practiced communal breeding with up to a hundred nests in a single tree. At the height of its population of three to five billion it may have been the most numerous bird on Earth, and A. W. Schorger believed that it accounted for between 25 and 40% of the total landbird population in the United States. Even today the Passenger Pigeon's historic population is roughly the equivalent of the number of birds that overwinter in the United States every year.
The Passenger Pigeon was nomadic and had no site fidelity, often choosing to nest in a different location each year. Pigeon migration, in flocks numbering billions, was a spectacle without parallel. John James Audubon described one flock he encountered with the words:
|“||I dismounted, seated myself on an eminence, and began to mark with my pencil, making a dot for every flock that passed. In a short time, finding the task which I had undertaken impracticable as the birds poured in in countless multitudes, I rose, and counting the dots then put down, found that 163 had been made in twenty-one minutes. I traveled on, and still met more the farther I proceeded. The air was literally filled with Pigeons; the light of noon-day was obscured as by an eclipse; the dung fell in spots, not unlike melting flakes of snow; and the continued buzz of wings had a tendency to lull my senses to repose... Before sunset I reached Louisville, distance from Hardensburgh fifty-five miles. The Pigeons were still passing in undiminished numbers, and continued to do so for three days in succession.||”|
Others frequently described these flocks as being so dense that they blackened the sky and as having no sign of subdivisions. The flocks ranged from only 3.3 ft (1.0 m) above the ground in windy conditions to as high as 1,300 ft (400 m). These migrating flocks were typically in narrow columns that twisted and undulated, but they were reported as being in nearly every conceivable shape.
The Passenger Pigeon was an excellent flyer, and is estimated to have averaged 62 mph (100 km/h) during migration. It flew with quick, repeated flaps that increased the birds velocity the closer the wings got to the body. It was equally as adept and quick at flying through a forest as through open space. A flock was also adept at following the lead of the pigeon in front of it, and flocks swerved together to avoid a predator. When landing, the pigeon flapped its wings repeatedly before raising them at the moment of landing. However, the pigeon was awkward when foraging on the ground, and used a "jerky, alert step" to move around. The pigeon bathed in shallow water, and afterwards lay on each side in turn and raised the opposite wing to dry it
At roosting sites the Passenger Pigeons packed so densely on branches that even thick ones often broke under their collective weight. They often piled on top of each other's backs to roost. The pigeons rested in a slumped position that hid their feet. They slept with their bills concealed by the feathers in the middle of the breast while holding their tail at a 45 degree angle. Dung could accumulate under a roosting site to a depth of over 1 ft (0.30 m).
If the pigeon became alert, it would often stretch out its head and neck in line with its body and tail, then nodded its head in a circular pattern. When aggravated by another pigeon, it raised it wings threateningly, but Passenger Pigeons almost never actually fought.
Nesting colonies attracted large numbers of predators, including american minks, weasels, american martens, and raccoons that preyed on eggs and nestlings, predatory birds, such as owls, hawks, and eagles that preyed on nestlings and adults, and wolves foxes, bobcats, bears, and mountain lions that preyed on injured adults and fallen nestlings. Accipiters and falcons pursued and preyed upon pigeons in flight, which in turn executed complex aerial maneuvers to avoid them; the cooper's hawk was known as the "great pigeon hawk" due to its successes, and cooper's hawks allegedly followed migrating passenger pigeons. It is believed that the large congregations of pigeons were based on the anti-predator benefits of very large numbers. While many predators were drawn to the flocks, individual pigeons were largely protected due to the sheer size of the flock, and overall little damage could be inflicted on the flock by predation. Despite the number of predators, nesting colonies were so large that they were estimated to have a 90% success rate if not disturbed.
In addition to predators, the Passenger Pigeon hosted at least two species of parasite. One species of phtilopterid louse, Columbicola extinctus, was originally thought to have only lived on passenger pigeons and became extinct with them. However, this coextinction was proven inaccurate by 1999 when Columbicola extinctus was rediscovered living on band-tailed pigeons. Another louse, Campanulotes defectus, was thought to have been unique to the passenger pigeon; however, it is now believed to have been a case of a contaminated specimen as the species is now considered to be the still-extant Campanulotes flavus of Australia. There is no record of a wild pigeon dying of either disease or parasites.
One of the primary causes of natural mortality was the weather, and every spring many individuals froze to death after migrating north too early. In captivity, a Passenger Pigeon was capable of living at least 15 years; Martha, the last known living Passenger Pigeon, was at least 17 and possibly as old as 29 when she died. However, it is unknown how long a wild pigeon lived.
The bird is believed to have played a large ecological role in the composition of presettlement forests of eastern North America. For instance, forests while the Passenger Pigeon was extant were dominated by white oaks. This species germinated in the fall, therefore producing acorns during the spring to be devoured and spread by the pigeons. The absence of the Passenger Pigeon's seed dispersal may have led to the modern dominance of red oaks. At roosting sites, few plants grew for years after the pigeons left. Additionally, the immense amount of dung present at these sites increased both the frequency and intensity of forest fires.
The formation of a nesting colony did not necessarily take place until several months after the pigeons arrived on their breeding grounds, typically during late March, April, or May. The colonies, which were known as cities, were immense, ranging from 120 acres (49 ha) to thousands of hectares in size, and were often long and narrow in shape. Due to the topography, they were rarely continuous. Since no accurate data were recorded, it is only possible to give estimates on the size and population of these nesting areas. The largest nesting area ever recorded was in central Wisconsin in 1871; it was reported as covering 850 sq mi (2,200 km2), with the number of birds nesting there was estimated to be around 136,000,000. In addition to these cities, there were regular reports of much smaller flocks or even individual pairs setting up a nesting site.
Courtship took place at the nesting colony. John James Audubon described the courtship of the Passenger Pigeon as:
The male assumes a pompous demeanor, and follows the female, whether on the ground or on the branches, with spread tail and drooping wings, which it rubs against the part over which it is moving. The body is elevated, the throat swells, the eyes sparkle. He continues his notes, and now and then rises on the wing, and flies a few yards to approach the fugitive and timorous female. Like the domestic Pigeon and other species, they caress each other by billing, in which action, the bill of the one is introduced transversely into that of the other, and both parties alternately disgorge the contents of their crop by repeated efforts.