The Great
Passenger Pigeon Comeback

The Great Passenger Pigeon Comeback is the flagship project of Revive & Restore’s de-extinction and genetic rescue efforts. Initiated in 2012, this project is the reason Revive & Restore took form. The project has evolved from an idea on a drawing board to a working collaboration of diverse partners and advisors united by a vision of changing the future of conservation.

Project Goal

The goal of passenger pigeon de-extinction is to restore cycles of regeneration to eastern American forests, making them more productive, diverse and bioabundant. Forest regeneration is spurred by disturbances, such as hailstorms, tornados, blizzards, brush fires, and historically, passenger pigeon flocks. Passenger pigeons and fire were the major sources of beneficial and continual forest disturbances for tens of thousands of years.

Since the extinction of the passenger pigeon humans have suppressed fires, leaving no consistent source of forest disturbance. While the eastern United States has experienced vast reforestation over the past 75 years, regeneration has virtually stopped, leaving new and old forest stands stagnant and their native inhabiting species on the decline. By reviving the ecological role of passenger pigeons we can restore and perpetuate forest regeneration cycles naturally.

This graphic depicts changes in the ecological community following a canopy disturbance – such as those historically created by passenger pigeon flocks. After a canopy disturbance an open canopy habitat allows sunlight to stimulate the successive colonization of grasses, flowers, shrubs, and thicket. Communities of insects, amphibians, reptiles, birds, and mammals all change as old trees regenerate, new trees germinate and mature, and the forest matures to a closed canopy once again.

What does regeneration do?

Forest regeneration supports greater diversity of tree species and produces a mosaic of woodland habitats from patch forests and shrub-scrub lands to savannah. This habitat mosaic supports greater diversity than a monoculture environment.

Oaks are one of the most important families of trees for eastern forest ecosystems and are dependent on regeneration cycles to flourish. Regeneration keeps oak stands young, which in turn boosts their rate of photosynthesis – putting more carbon from the atmosphere into the ecosystem. Young stands of oaks produce more acorns – the staple food of most eastern birds and mammals. Regenerating oak stands keep maples and competing trees from overtaking the community.

Eastern forests have evolved as disturbance ecosystems. The majority of native animal species use regenerating forest habitats to feed and raise young. Some animals, such as the New England cottontail, require these habitats for their entire life cycle. Many of these species are currently declining, threatened, or endangered.

Why the passenger pigeon?

Forest disturbances can be managed by humans through controlled fires and specialized tree harvesting, but these methods are costly in both funds and manpower, and often do not yield the beneficial impact intended. Controlled burns run the risk of becoming wildfires and damaging property, as well as threatening human lives. Dense flocks of pigeons offer an alternative solution to this problem.

Click on the tabs below, left to right, to see how a large flock of passenger pigeons produces a forest regenerating disturbance.

mature_forestA closed canopy forest prevents sunlight from reaching the forest floor, limiting the amount of plants that can grow.

disturbanceHistorically, flocks of passenger pigeons would arrive at a roosts or nesting sites and overcrowd branches and trees to the point that branches, limbs, and even old or small trees would collapse under the weight, spurring regeneration of new oak shoots and opening up the canopy to let sunlight reach the forest floor. The birds would consume food and outcompete rodents and deer in the area – both hosts of Lyme disease. A thick layer of guano would kill what understory plants were there and fertilize the soil for new growth. These events would last several days to several weeks and occur periodically every 3-5 years, rarely affecting the exact same patch of forest the same way twice.

regnerationThe next year in the absence of the pigeons the former roost or nesting site would become a first generation successional forest as the regeneration cycle started anew. This habitat would be thick in undergrowth – rich in both plant and animal species alike. This regeneration would continue toward a closed canopy forest until the pigeons came and started the process over again. No fire, hail, blizzards, or tornadoes necessary.

Other birds can’t substitute

The only wood pigeon currently in North America is the band-tailed pigeon. While the band-tailed pigeon and the passenger pigeon may appear to play the same ecological role, the traits that separate them make a big difference in how they impact the environment. Neither the band-tailed pigeon nor any other wood pigeon in the world are able to fill the ecological role of the passenger pigeon without some adaptation.

The different traits of the passenger pigeon each made the species uniquely adapted to living in crowded flocks. Without such high-density flocks, the passenger pigeons would not have caused the beneficial disturbances they did, no matter how many billions of birds there were.