Loon Update and Why Beavers Matter

2025, No. 12 — September 20th

Loon Update

At 14 weeks, Piper is looking more and more like a Loon. Her neck is longer and her bill larger.

As her wings have grown, she has that broader adult loon profile.

She spends a lot of time preening and stretching her wings.

Jon was fortunate to watch her practice using her wings to fly.

Her attempt at getting airborne didn’t quite work, but the landing was impressive.

How about that?!

Piper and her parents pretty much have the lake to themselves these days, and Piper is spending more time alone and further out on the lake, diving a lot. She can stay under 30 seconds to a minute, so it may be hard to keep track of her.

A Keystone Species Helping to Protect Pleasant Lake

Ecologists consider some species so valuable for the structure and functioning of natural communities and habitats that they are called Keystone Species. One such species is the Beaver (Castor canadensis). Once hunted nearly to extinction for their fur, beavers are being re-introduced all over North America, and the European species (Castor fiber) all over the UK, to help restore wildlife habitat, forests and groundwater supplies.

Some people see beavers as problematic. Let’s get to know them better. They are working for us to help protect the lake.

Beavers are best known for their dam-building skills. There are quite a few beaver dams on many of the streams and brooks coming into our lake. Each of them is helping trap rain-washed sediments and moderate the effects of flooding. Some of the dams provide pond and marsh habitat for fish and wildlife in the watershed.

Beaver dams are strong but leaky have been shown to be better at trapping sediment and regulating water flow than most human made dams. Two dams (below) hold back large bodies of water in the Pleasant Lake Watershed: Devils Half Acre Pond at the top of Great Brook and the pond at Esther Currier WMA south of Route 11.

 

Behind a beaver dam, a shallow pond fills with water, plants, and wildlife. Over many years, as sediment trapped by the dam fills the pond, its edges turn to marsh, then meadow, and finally to forest. If the beaver dams in our watershed were not there, Pleasant Lake would be receiving that sediment. Sediments washed into our lake are full of phosphorus from organic matter in the soils of the watershed. Adding lots of phosphorus to the lake will feed cyanobacteria blooms and eventually lead to greater problems for Pleasant Lake.

There is another important beaver dam in Turtle Cove.

Over the past few years, it has stopped several floods from bringing sediment and debris into the lake. Major spring floods have washed parts of the dam out over the past 5 years. Each time it was rebuilt differently by the beavers. Its structure now is much more secure. It held up well during a big rainstorm in early June this year.

From the front (above), it seems like a pile of sticks with water trickling through. The water in Great Brook and the cove is so low that Jon was able to get into the pond area behind the dam.  The back of the dam (below) is a sloping wall of mud, stones, and embedded sticks that has been made by the beavers from sediment and material trapped by the dam. At the base, it is over 10 feet thick! You can also see some of the exposed sediment that has accumulated behind the dam.

The dam does not cover the entire width of the cove. It doesn’t need to. Behind the dam is a forest with canals built by the beavers for moving themselves and branches around. As the beaver pond fills, water in those canals seeps slowly into the cove.

The forest in the cove is full of trees and other plants that do well in wet soils, and many are food for the beavers. That area is a breeding place for Wood Ducks, Hooded and Common Mergansers, and many songbirds. It is also home to otters, muskrats, and endangered Wood Turtles.  In total, the beaver dam collects sediment, helps hold water during floods, and releases sediment-free water gradually into the lake.

But what about the “harm” that beavers sometimes do?

Some beaver dams can cause undesirable flooding. Destroying the  dam or trapping out the beavers may stop that temporarily, but often beavers move back in and replace the dam. The town of Andover, near Pleasant Lake, had such a problem. The solution, saving the town thousands of dollars it was spending destroying dams and opening clogged culverts, was to install “beaver deceivers”. You can read about the problem and the solution here.

Beaver Deceivers allow regulating the water level in a beaver pond by using pipes and wire cages to move water in a way the beavers cannot plug up. If you look closely at the photo of the dam (above) at Currier Low Plain, you can see water bubbling out of the center of the top dam. That is a “beaver deceiver” pipe through the dam. A new one will soon be installed to further help regulate the water level. Note that the water flowing out of the pipe comes from near the pond surface and does not carry sediments.

Fine, but what about them cutting down big trees and my favorite backyard trees and shrubs? While most beaver food comes from plants in the pond and around the edges, they do sometimes forage further. When beavers cut down a big tree, it is mostly to get access to the bark. Below you can see an example from a nearby management area. It took several years to cut the tree down.

A year later, all of the bark they could reach had been eaten off. Tree bark is an essential food for beavers.

It is going to take a community-wide effort going forward to protect Pleasant Lake. Beavers are a vital part of that effort. They may cause damage to shrubs and trees in some yards, but that is a small price to pay for their help, and it can be prevented without harming the beavers or their dams. Here is a link to a website with lots of beaver information, including how to protect favorite trees from them – The Beaver Institute

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Bye for now …  Jen and Jon

Text and Photographs by Jen Esten and Jon Waage