You are what you eat: SFU researchers help uncover why passenger pigeons vanished

May 13, 2020

During the 1800s, passenger pigeons were one of the most abundant birds on Earth.

At their peak, it is estimated that there were 3 – 5 billion passenger pigeons roaming the skies of Canada and the U.S.A.  east of the Rocky Mountains. Their numbers were so large that people noted the sun would be blocked out for hours as flocks flew overhead. However, in the span of a few decades, passenger pigeons went extinct. The last passenger pigeon, named Martha, died at the Cincinnati Zoo in 1914.

Scientists agree humans wiped out the species, but they debate exactly how humans triggered their extinction. For years, scientists have suggested two theories to explain how humans caused this bird to vanish: overhunting or a lack of food due to deforestation. Researchers Thomas Royle and Dongya Yang in SFU’s Department of Archaeology, have helped unravel this mystery by examining the dietary ecology of these birds in an innovative study published in Quaternary Science Reviews.

In collaboration with colleagues at Trent University, University of Toronto Mississauga, and the Université de Paris, Royle and Yang used multiple biomolecular and archaeological methods to examine the diets of 90 passenger pigeon specimens recovered from 1000 to 120-year-old archaeological sites in southern Ontario and Quebec. Using stable carbon and nitrogen isotope analyses, a well-established tool for identifying the foods animals ate, they found a small number of birds primarily ate corn grown by local Indigenous peoples. DNA analyses and studies of the birds’ bone morphology indicate that corn consumption was not limited to pigeons belonging to a particular genetic or age group.

Their results suggests that passenger pigeons had flexible diets and could likely adapt to a lack of tree nuts from deforestation by consuming agricultural crops. This indicates overhunting, not a lack of suitable food due to deforestation, likely caused this once abundant species to vanish.

Since the 1970s, bird species around the world have experienced large declines in their numbers, and  many species now face extinction. Studies like Royle and Yang’s show how archaeology can be used to study the causes behind these declines and inform present-day conservation efforts. With a clearer understanding of our past, we can act now to protect our future.