A Surplus of Swans

I counted seven swans-a-swimming.

The beautiful birds were not a precious gift from my true love, as the holiday song suggests.  Instead, Mute Swans are quite common on Lake Allegan, which our home overlooks. Their graceful movement and luminous white plumage always command my attention. While not totally silent as their name implies, Mute Swans are blissfully quiet compared to the loudmouth Canada Geese that also frequent our lake.

And then there’s the ugly part: These lovely birds are invasive thugs.

Mute Swans came to North America from Eurasia in the mid-1800’s, intended as ornaments for private ponds and lakes. Escapees became invasive, out-competing other waterfowl, including our native Trumpeter Swans, for food. Mute Swans are also aggressive and known to attack, injure, and kill other birds.

Swans eat underwater weeds, known formally as submerged aquatic vegetation, or SAV. While ‘weed’ has a negative connotation, SAV is important for lake and pond health. It oxygenates and helps clarify the water and provides critical habitat for waterfowl, fish, and other lake dwellers. One Mute Swan consumes up to eight pounds of SAV per day. It uproots pounds more by raking the bottom with its feet and catching weeds while paddling. Bottom sediment then clouds the water, limiting light needed for weed growth.

In spring, Mute Swans can consume or uproot more vegetation than a lake or pond can regenerate before native waterfowl return from migration. Then, as vegetation tries to recover, the Mute Swan’s long reach gives it a leg up (a neck up?) over other weed dabblers like Mallard Ducks.

Speaking of that long neck, take a look at this bird’s extensive above-water reaching. I think you’ll see beauty that belies the swan’s unfortunate ecosystem role.
Now, back to those seven swans-a-swimming. A few years ago, that many swans—or ten or twelve—would have seemed a large number on our water. But for much of last summer, Lake Allegan was graced by swan herds up to fifty strong. I suspect we’ll see as many or more this year. Why? Here’s my hypothesis: It’s because the lake has been nearly rid of the common carp.

Since 2018, the EPA has removed more than 100,000 carp from our 1,600-acre lake. The project’s goal is to improve the native fish community and habitat. Carp are bottom feeders. Like the swans, they uproot aquatic plants when feeding and the resulting cloudy water hinders re-growth. The removal project seems to be working. Last summer, we noticed extraordinary weed growth, a welcome sign of a healthy lake, even as we and other boaters gnashed our teeth over clogged propellers.

I’m guessing the weed bonanza is what’s drawing Mute Swans in exceptional numbers. I imagine we’ll see even larger herds as the SAV continues to recover from the carp. That makes me wonder: Will the swans’ weed removal and sediment stirring reverse the post-carp habitat recovery?

So far, the number of Mute Swans we’re seeing is small compared to the 100,000 removed carp. But while fifty Mute Swans seem unlikely to threaten our lake’s ecosystem, there’s no shortage of Michigan Mute Swans waiting in the wings, so to speak: about 10,000 in the most recent (2019) count. That said, Michigan has a Mute Swan removal project underway. Its goal is to manage the population to fewer than 2,000 birds statewide by 2030. But the project is controversial.

Citizens often object when local governments take steps to restore habitats through swan removal. The removal policy does not allow hunting, but the Department of Natural Resources issues permits for removing the birds, their nests, and/or eggs. ‘Removal’ of a live swan means euthanizing it, using methods detailed in its policy statement. Michigan’s Audubon Society supports ‘humane, lethal removal’ of Mute Swans to allow native birds to thrive. Even so, it acknowledges the reason for controversy, noting in its position statement that Mute Swans ‘provide value by connecting the public to nature.’

The state removal effort is having an impact. There were 17,500 Mute Swans statewide in 2013. I recognize the conflict inherent in the removal project. But I’m encouraged by its implication for the long-term health of our lake, if the project’s success continues and our local population remains modest.

Meanwhile, a long-term Trumpeter Swan comeback project is also succeeding. This bird was extinct in Michigan—partly from Mute Swan competition—until the Kellogg Bird Sanctuary brought eggs from Alaska in the 1980s. The most recent count (2015) estimates there are more than 3,000 trumpeters in Michigan. Here’s an article with more info.

I see the occasional Trumpeter Swan, which always makes me cheer. Here’s a clip from 2019.

Distance and low light resulted in poor video, but you can see that the swans’ bills are quite angular compared to the Mute Swan. Migratory Tundra Swan bills are similar in shape, but the timing of this sighting makes me believe they’re Trumpeters.

I’ll continue to enjoy watching Mute Swans. Despite their invasive malfeasance, I may give them a cheer as well. That’s because they’re known to discourage geese. The honkers foul our neighborhood’s waterside park with their ubiquitous poop. If the swans have convinced even a few geese not to leave their little souvenirs, I’m grateful. I may even support our poop control needs by investing in a different kind of Mute Swan scare squad (say that four times fast!).  Mute Swan decoys can deter geese on both land and water.

Don’t they say imitation is the greatest form of flattery? Maybe Mute Swans aren’t such thugs, after all.

Resources 

First, a vocabulary note: I used herd repeatedly to describe a group of swans. That’s one of several collective nouns for the species. Others include bevy, game, and—when in flight—wedge.

Mute Swans are easy to identify from their bright orange bills and the large black knobs where their bills meet their faces. Trumpeter Swans lack the knob and have more angular bills, as mentioned above. For more information, check out the National Audubon Society’s free Field Guides: Mute Swan and Trumpeter Swan. Be sure to scroll to the audio files. You can listen to a Mute Swan’s snorts and growls as well as a Trumpeter Swan’s ko-ho, which is beautiful and really does sound like a trumpet.

A few articles about Mute Swans as invasive in Michigan:

Great Lakes Restoration Initiative: Managing Invasive Mute Swans in Michigan.

Michigan United Conservation Clubs: Mute Swan an Aggressive Invasive.

Related kids’ book

I hope readers share my posts with kids, so I often suggest related children’s literature. Here’s a great one for today’s post: Lakes and Ponds! With 25 Science Projects for Kids, by Johannah Haney, Illustrated by Tom Casteel. Published by Nomad Press.

The book shows kids how to be amateur limnologists—scientists who study inland waterways. They’ll learn how lakes and ponds form; about animals and plants living in them; water layers and how bodies of water change over time; and lots more. The book is filled with hands-on projects and experiments. For example, kids can find out why cold water sinks; make a water scope to observe a pond or lake’s underwater ecosystem; create a microclimate to observe the water cycle; and compare buoyancy provided by fresh and salt water.

The publisher suggests the book for kids ages 7-10 years, but I think older and younger kids can and will want to participate in its projects. Many require adult help, such as for cutting holes in plastic bottles. If kids in your life enjoy water activities like fishing or swimming or tromping at the water’s edge, this book will add to the fun. I learned a lot reading this book and plan to do several of its activities with grandkids who visit this summer.

Image Credits: Carol Doeringer, E. Spicer.