Once the most populous bird in North America—and perhaps the world—the passenger pigeon darkened the skies with immense flocks, their cobalt wings and peach-colored chests creating vast aerial spectacles. These flocks were so dense and lengthy that they could block the sun for days, while the collective sound of their wings was said to chill the earth below. Numbering in the billions, they vanished almost overnight, casualties of human exploitation.

In the 19th century, passenger pigeons became a cheap and abundant protein source. They were hunted mercilessly, netted, clubbed, shot, poisoned, and suffocated. By the time protective legislation was considered, few remained. The last passenger pigeon, a female named Martha, died in 1914 at the Cincinnati Zoo.

Today, scientist Ben Novak, in collaboration with Revive & Restore, leads “The Great Passenger Pigeon Comeback,” an ambitious de-extinction project. To revive a lost species, scientists need DNA samples and a closely related species. Fortunately, preserved specimens provide passenger pigeon DNA, while the band-tailed pigeon, a native relative in North America, offers a genetic match.

Since cloning doesn’t work with birds, researchers plan to collect primordial germ cells from band-tailed pigeon embryos—cells capable of producing eggs and sperm. By editing these cells to carry passenger pigeon genes and reintroducing them to the band-tailed pigeons, scientists hope to produce offspring with authentic passenger pigeon genetics. This means the first de-extinct passenger pigeon would have a band-tailed pigeon as its “parents.”

Novak’s research highlights the potential ecological role of passenger pigeons in the forests of eastern North America. Historically, when their flocks roosted, they disrupted forest landscapes by toppling saplings, breaking branches, and covering the ground in nutrient-rich guano. This apparent destruction was, in fact, essential to the health of these forests. The guano enriched the soil, allowing grasses, flowers, and shrubs to flourish, which then attracted insects, birds, and mammals. The passenger pigeons maintained this cycle, promoting biodiversity and productivity. In their absence, however, forest canopies have closed, limiting sunlight to the forest floor and diminishing ecological diversity. Bringing passenger pigeons back could restart this cycle, rejuvenating forest ecosystems and boosting biodiversity.

Reintroducing passenger pigeons on a large scale is critical to achieve the intended ecological effects. A few birds would be ecologically inconsequential, but flocks numbering in the millions would be required to truly impact forest dynamics. However, such vast flocks could also become problematic. Conservationist Mark Avery, author of A Message from Martha: The Extinction of the Passenger Pigeon, is skeptical. “This feels like an expensive vanity project, not real conservation,” he argues. Avery worries that the project may only produce a few passenger pigeons in captivity, repeating the species’ sad history of confinement rather than restoring a thriving wild population.

The debate over reviving the passenger pigeon raises critical questions about conservation, the ethics of de-extinction, and the feasibility of reintroducing species to transformed ecosystems. As scientists move forward, they’ll need to balance ecological ambitions with practical considerations and public readiness, hoping to avoid creating another chapter of captive sadness in the passenger pigeon’s legacy.

By Impact Lab