The Lake Where You Live

Loons look so calm and dignified when we see them on our lakes that it’s hard to imagine the number of threats they are facing.

Their nesting habitat has been shrinking in the face of development on lakeshores. Their water-edge nests can be swamped by waves from increasingly powerful boats. Some die from ingesting toxic lead split shot and jigs. Early in the nesting season, loons can be driven from their nests by hordes of blood-sucking black flies.

A decade or so ago a number of loons died in their migratory staging areas on Lake Michigan from an outbreak of avian botulism. More perished after the 2010 Deepwater Horizon oil spill in the Gulf of Mexico, where many loons spend the winter.

A couple of springs ago, some loons on their return migration fell out of the sky while flying through a mix of ice and rain and unstable air currents. Meanwhile, the Audubon Society says that loons’ breeding territory is being pushed north by climate change.

And that’s not to mention declines is successfully fledging young loons, an issue apparently related to declining water clarity on our lakes, in turn connected with a warming climate and more heavy rainstorms that wash nutrients into the water, stimulating the growth of algae. Loons feed by sight, and in murkier water it’s harder for them to find and catch fish to feed their young.

Now, Walter Piper, lead investigator on The Loon Project in northern Wisconsin and Minnesota, has aimed the spotlight at a new concern—and again it relates to water clarity. Loons on their first migration don’t necessarily have it easy in the saltwater of their winter environment.

In a recent post on his website (www.loonproject.org), Piper reports that only 13 of 209 chicks banded in Wisconsin between 2017 and 2020 (6.2%) have returned as adults. That led him to ask why, and for the answer he looked to Florida. 

To make a somewhat long story short, he looked at data on variables including water clarity, temperature, pH, salinity, dissolved oxygen, nitrogen, phosphorus, and chlorophyll A. That last parameter provided a clue. 

Piper found that first-year loons were much less likely to return to the northern lakes where they were bred if chlorophyll A levels in Tampa Bay were high during December. 

Chlorophyll A relates to the amount of algae in the water. “A very high level “can indicate an algal bloom, which reduces water clarity and can lead to loss of oxygen and release of toxins,” Piper writes. Its negative effect occurred only in the December after a loon’s first migration.

“We would expect these neophytes to be at risk during this period, because they must suddenly find new aquatic prey in wholly unfamiliar habitat,” Piper adds. “High algal levels add another layer of difficulty to foraging, likely reducing the abundance of prey as well as a loon's ability to find them.”

He cautions that the Chlorophyll A data is from only one part of loons’ winter range; it would mean more if it covered all of Florida's Gulf Coast. In other words, this finding alone doesn’t explain why so many juvenile loons are failing to survive. Piper concludes, “It is urgent to learn what is killing them. I will keep looking.”

So, when we think of loons and all that besets them, we could metaphorically imagine the species as placid and serene on the surface, but under the water, paddling like mad.

Ted Rulseh resides on Birch Lake in Harshaw and is an advocate for lake protection and improvement. His Lakeland Times and Northwoods River News columns are the basis for a book, “A Lakeside Companion,” published by The University of Wisconsin Press. Ted may be reached at [email protected].