We are coming up on the 100th anniversary of one of the sad days in ornithology.  On September 1, 1914, the last remaining Passenger Pigeon, a female named Martha, died in captivity in the Cincinnati Zoo.  A species that had been astoundingly abundant had vanished from the earth.


Photo of Martha taken by Carl Hansen, Smithsonian Insitution, 1985.

Passenger Pigeons had a large range in eastern North America, spanning eastern Canada south to the Gulf coast and west to western Texas and Montana.  They resembled the Mourning Dove but were much larger, up to 17 inches long.  Their feathers glowed with red, gold and blue iridescence.  The word passenger in their name refers to their migratory tendencies, not to their use in carrying messages for humans.

Passenger Pigeons were undoubtedly once the most abundant bird in North America.  In the early part of the 19th century, Passenger Pigeons were more abundant than all other North American birds combined!  There is a report of one flock that contained over two billion birds.   Audubon reported a migrating flock of Passenger Pigeons in Kentucky that blackened the sky for three days.  Some nesting colonies were 20 miles across.  Such numbers boggle the mind.

In Maine, Passenger Pigeons were summer residents.  They were abundant until 1820 or so and were common enough to provide successful hunting until around 1850.  The first record we have of Passenger Pigeons in Maine dates from the French explorer Samuel Champlain who found them on islands near Cape Porpoise in what is now York County.

Why did this species go extinct?  The answer is probably obvious: humans.  A large industry developed in the 19th century to provide Passenger Pigeon meat for the tables of European immigrants to the United States.  Because of the pigeons’ flocking and colonial nesting behavior, they were easy targets.  Large numbers of pigeons could be harvested with ease.   Some were caught in nets, others fell to the ground after being smoked with sulfur fires, yet others were killed by guns.  Special guns, precursors to machineguns, were developed to allow large numbers of pigeons to be killed quickly.

The harvest of what seemed like a nearly infinite resource was not regulated.  The development of railroads, providing a fast way to get pigeon meat to eastern markets, drove the hunting to an even greater intensity.   By the middle of 19th century, several thousand people derived a livelihood from harvesting and selling Passenger Pigeons.  One processing plant in New York handled 18,000 birds a day.  A billion birds were harvested in a single year in Michigan.

But how could the most abundant bird in North America be harvested to extinction?  As the population started to decline, one would expect the industry to collapse, giving the ravaged Passenger Pigeon population a chance to recover.  The answer appears to lie in the highly social nature of the species.  The gonads of most birds regress to about a fraction of their active size during the non-breeding season.  Changing day lengths cause birds to increase their sex hormones and their gonads enlarge.  Rather than increasing day length, the cue for Passenger Pigeons to enlarge their reproductive organs and initiate nesting was the social stimulation of lots of other Passenger Pigeons in a local area.  Without a large enough concentration of birds, the reproductive cycle did not begin.

The collapse of the Passenger Pigeon started around 1880 and commercial hunting, no longer profitable, ceased.  Unfortunately, the large flocks of Passenger Pigeons were dispersed across the continent in smaller groups.  These flocks may never have gotten large enough to induce the beginning of the nesting cycle.

The population continued to decline and was extinct in the wild until 1900.  The last Passenger Pigeon reported in Maine was shot in Dexter in 1896.  Efforts to breed the species in captivity failed.  Martha was the last of her species, gone 100 years ago.

[Originally published on August 17, 2014]