Most people are familiar with the story of the passenger pigeon – its giant flocks and the harvests and deforestation that lead to its swift demise –but our general understanding of the passenger pigeon is fraught with misconceptions. Some of these misconceptions have become canon of the species, despite lack of evidence or contradictory evidence. The best way to get to know the passenger pigeon is to address these misconceptions with the most up to date knowledge of the species.
Misconception 1: Passenger pigeons were not abundant before the arrival of Europeans to North America.
This idea was put forth in the 1980’s to address the seeming lack of passenger pigeon bones in archeological sites in the northeastern United States. The assumption was that if there were billions of passenger pigeons in the past there should be many bones – but often Turkey and other bird remains were more numerous that pigeon bones in historic Amerindian village sites.
The notion put forth to answer this was that: 1) Amerindians were major competitors of acorns and resources to passenger pigeons, keeping their numbers in check; 2) Europeans arrive and through warfare and disease decimate the Amerindian population, which relieved competition for acorns and allowed the passenger pigeon population to boom.
Abundance of archeological remains do not reflect actual population sizes accurately, the only thing they actually indicate reliably is the presence of a species during a given time period. In fact using the same study technique another analysis found that passenger pigeons were abundant in the Southeastern United States prior to European arrival.
Our current population genetics analyses show that passenger pigeon effective population sizes were very large for many thousands of years.
Misconception 2: The passenger pigeon required huge flocks to survive.
This misconception is completely contradictory to the first misconception, though both notions are often cited. This idea is that passenger pigeons evolved to live in huge flocks and became dependent on this population biology – in other words they could not produce enough offspring to survive unless there were billions of them, either for social reasons (they would not breed in small flocks), or predator reasons (they could not satiate predators without huge flocks), or for resource reasons (they could not find adequate food sources in small populations)
Passenger pigeons were observed breeding in single pairs and flocks of dozens during the 1800’s. Some of the last passenger pigeons collected from the wild were juveniles, proving that when there were only a few hundred birds left in the world they were still producing offspring. However it is unknown whether or not the birds could have rebounded, because persecution of the species never relented as they became rare. In fact, harvesting of passenger pigeons only intensified as they became harder to find.
Our current population genomics of the species indicate that the species went through periods of small population size and was able to rebound to large population size quickly. What we’ve learned is that the passenger pigeons ecology allowed it to be flexible to many states of existence.
Misconception 3: Passenger pigeons were dependent on a diet of acorns.
The hypotheses proposed by previous studies (as recent as 2014) have often assumed that the main food source of the passenger pigeon were acorns, meaning that the species was dependent on the presence and abundance of oak trees.
While acorns are the most cited food source, passenger pigeons were observed to eat over 42 genera of plant seeds and fruits, and from time to time consumed insects. It was a superb generalist. Knowing that the species was abundant for thousands of years, we now know that the passenger pigeon was abundant during periods of history in which oak trees were scarce – meaning that the birds could not be dependent on them as their main food source. Their generalist diet allowed them to thrive even when the environment changed.
Misconception 4: The passenger pigeon was naturally vulnerable to extinction.
This has been proposed many times, using support from misconceptions 2 and 3 to explain how billions of birds disappeared so quickly – and ultimately has been used for over a century to absolve humanity from causing the extinction of the passenger pigeon.
Given what we’ve learned through studying population genetics we can re-evaluate historic accounts with a more accurate understanding of passenger pigeon ecology – the end result is that the passenger pigeon does not actually exhibit any of the traits commonly associated with vulnerability to extinction. The species generalist diet, nomadic flocking, and ability to rebound from low numbers made them very resilient to environmental change. The passenger pigeon was a “super species”. Had humans not commercially harvested passenger pigeons at the same time they deforested America the passenger pigeon would certainly still be alive today.
The Passenger Pigeon,
by A.W. Schorger, 1955
Schorger’s book is the seminal treatise of passenger pigeon natural history. Though dated, the majority of the content is still robust when viewed through more recent discoveries and research.
A Feathered River Across the Sky,
by Joel Greenberg, 2014
Greenberg, the leading living expert in passenger pigeon history, not only brings Schorger’s work up to date, but enriches the lore of the passenger pigeon with the human stories that and shaped the fate of the species.