In the 19th century, billions of passenger pigeons crowded the skies of North America. By 1914, the birds had become extinct. Previously, ecologists thought human activity was responsible for the passenger pigeon’s sudden, rapid demise. Now, Shou-Hsien Li of National Taiwan Normal University and colleagues have found that changes in environmental conditions may have caused passenger pigeon populations to fluctuate dramatically. A natural decline in population, combined with human activity, may have resulted in extinction. The research appears in the Proceedings of the National Academy of Sciences.
In the 1800s, observers reported flocks of passenger pigeons blanketing the sky. James Audubon, the artist and ornithologist, once described a flock of passenger pigeons blocking the sun for three consecutive days. Population estimates for the beginning and middle of the 19th century ranged from three to five billion.
Within a human lifespan, the species was extinct. What caused the birds to disappear so suddenly? Previous researchers blamed human hunting and deforestation.
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