Pennsylvania is a hard state for beavers. We know only two supporters from that area. Mostly beavers are killed whenever they are seen. And even when it is noticed that their ponds help wildlife, like in this recently reprinted report from 1999, the appreciation is still pretty thin. Like Bilbo’s famous toast quote.
“I feel thin, sort of stretched, like butter scraped over too much bread.”
The Life of a Pond
On the margin of the lake where the feeder streams converge are a string of beaver ponds like tourmaline jewels. We paddle softly as we approach, portage neatly over the dam. We hardly notice its intricate web of mud and sticks, how with a minimum of materials it holds back the current and flattens it into a pool. We’re not here to appreciate beavers (they’re so secretive we rarely see them). We’ve come to the beaver ponds on this spring day to see ducks.
Of course we’re not here to see those nasty invisibeavers. No one ever sees them but weirdos and fishermen.
Beaver ponds are fine places for waterfowl, a recent study funded by the Pennsylvania Game Commission and the Penn State Cooperative Wetlands Center has confirmed.
“The Game Commission was particularly interested in waterfowl broods—mothers and their chicks,” says Diann Prosser, a graduate student in wildlife ecology who with Robert P. Brooks, professor of wildlife and wetlands, investigated beaver pond succession—the stages a pond goes through during its life span.
You don’t say. Beaver ponds are good places for birds! Get out! Next you’ll be telling me they’re good places for fish and frogs too! How much rubbish do you expect one woman to believe?
Beaver ponds are active for about 30 years. The first stage (which Prosser calls “new active”) begins when a stream is dammed and a pond forms. The trees and bushes, their roots drowned, give shade and leafy cover. Eventually they die and rot (or are cut down and eaten, depending on their size and species). Then the beavers must travel further afield to forage, and the dam is widened and the pond enlarged, during this “old active” stage. Trunks and stumps dot the pond, but few shade trees remain except on the edges. The pond is carved with channels, a mix of open water and shrubby hummocks. After the beavers leave the “abandonment” stage—the dam eventually breaks and the water subsides. Grasses and shrubs recolonize the pondflats, and slowly it returns to woodland.
I am sure this happens sometimes. But it’s always bothered me that this idea of beavers eating their way out of house and home doesn’t take into account that as the pond grows conditions improve for more aspen or willow or cottonwood. That’s why beavers are called ‘willow farmers’ by some. They eat willow and their actions increase the very thing they need most.
Unlike, oh say, humans.
Prosser and Brooks surveyed beaver ponds in all three stages, looking not for beaver but for birds. They found all six of Pennsylvania’s common waterfowl breeding on beaver ponds: Canada goose, wood duck, greenwinged teal, American black duck, hooded merganser, and mallard. “New active” ponds and “old active” ponds produced the most waterfowl. Geese seemed to prefer the older, more open ponds; while wood duck, hooded merganser, and black duck liked newer ponds with more cover.
Whether you look at the beginning, middle or the end, beaver ponds are havens for wildlife. And here’s a corollary: killing beavers is bad for bird and wildlife populations. Capeesh?
Marsh and song birds also frequented beaver ponds. The American bittern and Virginia rail, both secretive waders, were found in older ponds, as were the alder flycatcher and redwinged blackbird. The Louisiana waterthrush and Acadian flycatcher visited active ponds; the swamp sparrow, common yellowthroat, and veery lived in all three pond habitats.
“A beaver pair’s goal in building a dam is to create a pond where they can build a lodge, hide from predators in the water, raise offspring, and store food for the winter,” says Prosser. “In the process, they are creating a variety of wetland habitat for waterfowl and other birds.”
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