- Dams threaten the nesting habitat and food resources for many species of birds.
- The Nature Conservancy works with river managers to minimize the impacts of dams for wildlife and people.
- Different species of birds depend on a healthy river system created by natural, seasonal river flows.
By Margaret Southern
The Belted Kingfisher may be known for its fishing abilities — they don’t call them “kingfishers” for nothing — but its nest-building skills could be considered equally impressive. Using its feet and thick beak, a kingfisher can spend hours digging into exposed riverbanks to create a 3- to 6-foot-long tunnel in which to nest.
Luckily for the kingfisher, these nesting spots are easy to find along riverbanks. Or, at least they used to be.
The seasonal highs and lows of a river create the fresh, steep banks in which the birds excavate their nests. But as more and more dams crop up on rivers, the number of rivers that experience these natural highs and lows is diminishing.
The disappearance of the kingfisher’s favorite nesting spot is just the beginning of the problems that the loss of this essential river function can cause. The Nature Conservancy is working with river managers around the world to minimize the ecological and social impact that dams and other river diversions can cause.
Going With the Flow
The natural flow patterns of a river become the heartbeat of an entire ecosystem.
The low, calm water that fills in a floodplain becomes a temporary nursery for many species of fish — and a source of food for birds and other inhabitants of the forest. When the water moves back out of the floodplain, it leaves behind nutrients that allow native plants to grow.
It’s from exposed perches on these plants that the kingfisher stalks its prey. The hunter will wait patiently until it sees a fish underwater, then quickly dives in to snatch its prey. Flooding helps the kingfisher in this endeavor, too. Plants in the floodplain filter out pollutants, sending cleaner — and clearer — water downstream. Dammed rivers can also cause significant changes in fish populations, making it harder for these birds to find enough of the right kinds of food.
“People don’t normally think of birds when they think about the impact of dams,” says Dave Mehlman, director of the Conservancy’s Migratory Bird Program. “But a healthy, living river with natural highs and lows is inextricably linked to the health of local bird populations.”
And it’s not just fish-eating birds that feel the effects of a dam upstream. From ducks and shorebirds to warblers and flycatchers, many birds depend on a healthy river system. For example:
- The Wood Duck inhabits riparian floodplain forest, which is dependent on natural river flows. Flooding not only helps keep its habitat intact, but gives the duck greater access to the forest and a primary food source — acorns, seeds and fruit.
- The dazzling Prothonotary Warbler nests almost exclusively in southeastern swamp forests, such as those found along the Savannah River, using cavities in older trees and branches near water. It lines its nest with mosses and insects that also depend on a healthy river system.
- The Willow Flycatcher and many other birds in the southwestern U.S. depend on dense riverside willow thickets for nesting habitat, food and protection from predators. Natural flood cycles renew the thickets, keeping them from getting too old and dense for the birds.
Recreating Healthy Flow Patterns
As the world’s demand for energy continues to grow, more dams and infrastructure projects are inevitable. So the Conservancy is using science to solve the complex problem of how to minimize the impacts dams can create for wildlife and people.
For example, in 2005, the Conservancy began working with the U.S. Army Corps of Engineers to time the release of water from the Alamo Dam on Arizona’s Bill Williams River to mimic natural, seasonal flow patterns. Controlled releases provide the necessary conditions for native fish as well as the growth of young cottonwood and willow seedlings, creating future habitat for birds such as the Willow Flycatcher.
Striking a Balance
Internationally, the Conservancy is working with the International Hydropower Association, the World Bank and others to integrate ecological health into decisions affecting the placement, design and operation of existing and future dams.
“The world has put a lot of demand on rivers without really thinking about the ecological consequences, and this has led to loss of freshwater resources that animals, plants and people need,” says Jeff Opperman, the Conservancy’s senior advisor for sustainable hydropower. “But there is a better way. What we’re doing now is making sure ecological health is fully integrated into what were previously primarily engineering decisions."
By expanding this work in river ecosystems worldwide, the Conservancy hopes to protect the habitat that kingfishers and many other birds depend on far into the future.