Humans not entirely at fault for passenger pigeon extinction

Cotinis

Once the most numerous bird species in North America, passenger pigeons went from numbering in the billions to being extinct in less than a century. Their decline has been mostly blamed on intensive hunting. But new research suggests that the human impact coincided with a natural decrease in population size, resulting in Martha, the last passenger pigeon, dying in 1914.

Robert Zink, from the University of Minnesota, describes the story of a billion passenger pigeons passing one spot during a migratory passage. He estimates that it meant “nearly 400,000 birds per minute, stretching across the sky." Flocks could block the sunlight for hours as they moved in mind-boggling numbers. On the ground, the passenger pigeons ate acorns, beechnuts, and chestnuts but also soft fruits.

Regan Early, lecturer in conservation biology at the University of Exeter, said, “They were a keystone species that had incredible effects on the landscape. They came, dropped bird poo everywhere, and devoured the fruit crops in the forests. Their excrement was toxic to plants, and when a flock roosted on trees, they could break all the branches through the sheer numbers perching."