Battle for the Island: Beavers versus Herons

Beaver teeth marks on tree
- Photo Credit: Francesca Gross
Green Heron
- Photo Credit: Greg Harber
Yellow-crowned Night-heron
- Photo Credit: Greg Harber

In the northern corner of East Lake, there’s a small island with a few large trees. There’s a battle – of sorts – going on between herons and beavers for the use of these trees. Until recently, the beavers had been winning, but now the herons have some help. Here’s what’s going on…

Many large, water-loving birds such as herons (tall, long-legged birds with sharp beaks they use to catch fish and crayfish) and geese like to nest on islands. This gives them protection from foxes, raccoons, opossums, and other predators that do not like to swim. Any of these predators would quickly devour a nest full of eggs or young birds if given a chance.

East Lake’s island has long been a favorite nesting location for Great Blue Herons, Yellow-crowned and Black-crowned Night Herons, and Canada Geese.  While the geese nest on the ground, the herons build nests in the branches. All was fine until the beavers arrived.

Beavers eat plants – not only those growing along the water’s edge, but also plants growing nearby. This can include trees. With their sharp teeth, they easily chisel through the outer bark at the base of large trees and then eat the nutritious inner bark. Trees begin dying back as they lose their inner bark. If the tree is small enough, the beaver will cut it down by chewing through most of the wood near the tree’s base. The beavers then eat the leaves and the inner bark of branches on the fallen tree.

In addition to being accomplished lumberjacks, beavers are also famous for building dams across creeks to flood areas upstream. Beavers harvest vegetation in the flooded area and then float the vegetation back to their lodge.

Beavers were widespread on the continent before trapping and the demand for beaver fur led to their near-extinction in the 1800s. Thanks to the work of early conservation biologists, the beaver was saved from extinction and was re-established in much of its original range by the mid-1900s.

While beavers play a beneficial role in natural ecosystems, their role in the human-altered landscape can be good or bad. In urban areas, beavers can provide habitat diversity (such as ponds) that helps some wildlife species. On the other hand, the flooding they create can damage property and disrupt human activities. Another problem is their hunger for trees. And this leads us to the battle at East Lake.

As part of their modern population expansion, North American Beavers have returned to Jones Valley. And they are hungry. They’ve moved into all of the city’s major streams, including Village Creek. The beavers that have taken up residence at East Lake Park have begun gnawing on the bark of the island’s trees. Some trees have been toppled by the beavers, while others are dead or dying. As a result, herons now have fewer places to nest.

Neither the beavers nor the herons are species vulnerable to extinction.  But while there is plenty of habitat for the beavers in the area (whether we like it or not), there is very little good nesting habitat for herons. For this reason, the Birmingham Audubon Society (BAS) stepped up to protect the trees from the beavers.

With the approval of the Birmingham Department of Parks and Recreation, and with funding from the National Audubon Society and the South East Lake Neighborhood Association, BAS wrapped the base of the trees in sturdy wire mesh to prevent beavers from killing the trees. For those tempted to feel sorry for the beavers, rest assured they are finding plenty of food in nearby areas along Village Creek.

-R. Scot Duncan