Passenger Pigeon numbers fluctuated greatly, increasing the bird’s extinction risk

8/15/2014 | 0

Lewis-Cross-PAPI-art

Passenger Pigeons amass in trees and stream over a river in a 1934 painting by Michigan artist Lewis Luman Cross. Courtesy of Grand Rapids Art Museum

A novel study of the population history of the extinct Passenger Pigeon suggests that the bird was not always as populous as it was in the 1800s, when it is believed 3-5 billion individuals roamed North American forests.

Researchers from Minnesota and Taiwan conducted the analysis using DNA extracted from the toe pads of three pigeon specimens and published their results in the Proceedings of the National Academy of Sciences.

Read the abstract.

About 500,000 years ago, write the researchers, the species likely numbered in the billions, but 21,000 years ago, when glaciers covered a chunk of North America, the population had fallen to perhaps a few million.

By 9,000 years ago, after the glaciers had receded, the pigeon had recovered, but annual variations in the production of acorns, a primary food source, led to vast swings in the bird’s population: For the last 6,000 years of its existence, numbers ranged from lows of 60 million-1.7 billion to highs of 6.7-8 billion.

The fluctuations resemble those of so-called outbreak species such as locusts or lemmings, the scientists say. The pigeon was able to withstand the ping-pong nature of its population only until it encountered European settlers and their descendants.

An article in our February 2014 issue describes how an unrelenting slaughter of pigeons in the late 1800s wiped out the species in a manner of decades. The last Passenger Pigeon died in captivity in a zoo 100 years ago, on September 1, 1914.

Read the article “Like Meteors from Heaven,” by Joel Greenberg

See a timeline of the Passenger Pigeon’s extinction.

“We suggest that before human settlement, the Passenger Pigeon routinely recovered from population lows,” the scientists write. “We hypothesize that a downward trend in its population size occurred simultaneously with human exploitation in the late 1800s and that the combination of the two triggered its rapid extinction. Once below a minimum threshold population size, the conspicuous roosting and breeding behaviors of this bird could prevent its recovery.”

About the painting and the artist

Lewis Luman Cross (1864-1951) lived most of his life in the small western Michigan town of Spring Lake, south of Muskegon. Although he had only six months of formal art education, he produced 500-600 paintings during his lifetime. He painted scenes of wildlife, seascapes, hunting and fishing, and local historical events.

Cross is best known for his images of Passenger Pigeons. When the birds were still abundant, he shot one and mounted it; the specimen was the model for many of his paintings. He once said that in the 1870s, when a flock passed “the sun would be obscured for as long as an hour. At other times, when the sun was in the right position, a flock would appear as a perfect rainbow caused by (the birds’) iridescent coloring.”

Cross completed the painting above, Bird’s Eye View of Passenger Pigeons Nesting, in 1934. “The oil painting, executed in autumnal colors, depicts flocks of pigeons as they come to nest in the trees along the riverbank,” according to the Grand Rapids Art Museum. “Men, possibly hunters who helped to drive the birds to extinction, are seen prowling in the woods as more birds fly in formation overhead.”

The painting and one other by Cross, simply titled Passenger Pigeons, can be seen at the Grand Rapids Art Museum.

A version of this story appeared in the October 2014 issue of BirdWatching magazine. Subscribe.