Loons are one of the most noticeable species on local lakes and many residents and visitors are interested and concerned about their success.
Erica LeMoine, Northland College Loonwatch and Citizen Science Coordinator, talked about loons at the 21st annual Northwest Lake Conference June 21 at Hayward Middle School.
Worldwide, she said, there are 640,000 loons, and 96 percent are summer residents of Canada with only 4 percent in the U.S., along with small populations in Iceland and Greenland. Loons in Wisconsin are counted in a statewide Wisconsin survey every five years and annually by 196 lake monitoring volunteers around the state. The Wisconsin survey looks at chicks and adults on preselected lakes only.
The 1985 survey found 2,400 loons. By 2015 the number had increased to 4,350, showing a growth of roughly 1 percent a year.
But LeMoine said the future for loons looks gloomy, as based on changes in temperature and precipitation related to climate change, the Audubon Society has predicted that by 2080 loons will lose 56 percent of current summer range and 75 percent of current winter range.
The Audubon model projects that by 2080 the only remaining loons in the Upper Midwest might be in northern Minnesota.
Citing a specific climate change phenomenon, LeMoine said extreme rainfall events since 2012 have endangered loon nests. Another threat to nesting loons, she said, is boat wakes that wash over nests, endangering chicks.
LeMoine also reviewed insights from loon research.
Based on visual banding reporting, she said, it was found that female loons are more loyal to their territory than their mates. For example, when an intruder male fights an established male and is victorious, the female stays with the intruder on that lake versus leaving with her former male partner.
Another finding is that loons will migrate back from the south to a lake that is within 22 kilometers of where they were born. If they were born on a seepage lake (no inlet or outlet), they will return to a seepage lake. If they were born on a flowage lake (with inlet and outlet), they will return to a flowage lake.
Research has also shown that 96 percent of local adult loons migrate by staging on Lake Michigan from mid- to late-October for an average of 27 days, where they fatten up for the flight south.
One issue that has surfaced on Lake Michigan is the loons are eating an invasive fish that itself eats invasive mussels that filter a dangerous bacteria from the water. As a result, several loons have died.
Once loon chicks are ready to migrate south, they make a straight beeline for the Gulf of Mexico, taking about five days to make it to the Gulf. In their winter range, she said, loons move from the Gulf of Mexico up the East Coast toward Maine and back.
Once chicks have migrated south, they will stay away for three years before they return to their northern lakes. LeMoine said researchers believe the chicks wait until they are larger so they can compete for territory and sexual partners once they return north.
Because loons eat fish that can have mercury in their tissues, loons further concentrate the mercury in their bodies. Mercury negatively impacts their reproduction — when mercury levels are higher, fewer chicks are born.
Lastly, LeMoine played recordings of loons demonstrating that the calls of older, smaller-bodied adult males have a lower pitch than heavier and younger male loons.