By Katherine Boyk
Special to The Lakeland Times
Loons are a beloved species in northern Wisconsin.
In addition to their striking looks, captivating calls, and popularity on souvenir merchandise, loons have a special significance in Vilas and Oneida counties as the subjects of two long-term studies. And the loon population here is leading researchers to some significant findings.
“Aside from being glamorous and well-loved, loons are a great species for tracking settlement patterns because they are long-lived and they don’t move far from their birth lake,” Dr. Walter Piper said. Piper is the principal investigator for the Loon Project, based in central Oneida County. Piper focuses his research on how loons seek out, acquire, and defend their territory.
Another study in Vilas and surrounding counties, headed by Dr. Mike Meyer, a research scientist and wildlife toxicologist for the DNR Science Services, examines the effects of mercury on loon survivorship and reproduction.
The Lakeland region is fortunate to be home to the second largest loon population in the Midwest, according to Meyer. This area is especially good for studying loons because they are accustomed to the presence of people and allow researchers to approach closely, which is important for collecting data.
Piper and Meyer both report that the local loon population is doing well and has been increasing slightly in recent years. Adult survivorship is high and more than half of chicks born here return to the area as adults after two to four years, according to Meyer. Because of the growing population, loons have been colonizing new lakes and territories.
However, Meyer is concerned about high loon mortality during migration in recent years. Low lake levels and aquatic invasive species in the Great Lakes have spurred a rise of botulism E, which sickens loons that eat infected fish. During the 2012 fall migration, 1,500 dead loons were recovered from Lake Michigan, including four or five from Meyer’s study.
This spring’s late ice-out also meant that loons couldn’t return to their territories until two or three weeks later than usual, which delayed nesting or may have caused some pairs to not nest, according to Meyer. Nevertheless, Piper says that 2013 was a “big year for chick production” in Oneida County. The Loon Project captured and banded 87 chicks and 82 adults this summer – a record number.
Banding reveals much
Both Piper’s and Meyer’s studies involve banding loons. Each bird is given a unique combination of four colored bands, two on each leg. Field workers can then identify individuals as they return from migration each year, settle on a territory, raise chicks, and interact with other loons. Since research began in 1991, more than 3,600 adults and chicks have been banded in the area, according to Meyer. This year, a loon that was banded on Little Bearskin Lake in 1991 was seen in Oneida County. He is at least 26 years old.
The banding system enabled researchers to disprove one of the most common misunderstandings about loons. It turns out that they do not mate for life. Rather, loons typically have three to five mates during their lifetimes, according to Piper.
It is not uncommon for loons to battle over territory ownership. An intruding loon will fight with one of the loons that lives on a lake. The victor will remain on the lake and the loser may fly to another lake and attempt to settle there. Both males and females will battle over territory, but Piper’s research has found that only males will fight to the death.
This territorial behavior is a key component of Piper’s study. By tracking loons as they move from lake to lake, he is examining habitat selection and territory settlement. Piper has found that loons tend to choose lakes that are similar in size and pH to the lake on which they were born. This may be because they are more genetically adapted to the habitat or because they have learned behaviors, such as how to catch fish, that are suited to a specific type of lake.
Piper is now examining whether this learning continues throughout a loon’s life. He hypothesizes that when choosing a new territory, adult loons may seek out lakes that are similar to ones where they’ve successfully produced chicks in the past.
These findings are revolutionary in understanding habitat selection. Previously, ecologists thought that there is a specific sort of high-quality territory that all members of a species compete for, but Piper’s research suggests otherwise. “There isn’t one overriding ‘good’ territory,” he said. “Rather, individuals have their own preferences based on their past experiences. They learn what a good territory for them may be.”
And these findings are applicable to many species, not just loons, according to Piper.
“It is extremely important for conservation to know how animals choose habitats. This has many implications for restoration and wildlife rehabilitation,” he said.
More information about Piper’s study can be found at loonproject.org.
Mercury and loons
Meyer’s research is also concerned about the conservation of loons and other fish-eating species that are vulnerable to mercury toxicity. Mercury is released into the atmosphere from coal-burning power plants and then settles into lakes. The toxin magnifies as it rises through the food chain, so fish-eating species, including humans, are exposed to the most mercury.
Loons are especially vulnerable to mercury because they eat fish exclusively and often nest on small seepage lakes, which tend to have higher mercury levels. Meyer has found that loons nesting on these lakes have three to five times as much mercury in their blood and eggs as those on large drainage lakes.
“If mercury were removed from the Wisconsin environment, the popula-tion growth of loons could be higher,” Meyer said.
Previous studies linked mercury with a suppression of immune function and neurological capability in loons. Developing embryos are especially sensitive to mercury, so high levels may reduce hatching. Meyer has found that loons on small seepage lakes are less successful at producing chicks, though other factors such as limited food resources may contribute to this as well.
In 2008, the Wisconsin DNR passed new regulations requiring large coal-fired power plants to reduce mercury emissions by 90 percent by 2021. These regulations were passed mostly due to concern about human health, but the environmental impact of mercury exposure on fish-eating wildlife was also considered.
The new regulation won’t eliminate mercury – which is a global pollutant – in local lakes but Meyer “anticipates improvement” as deposition into lakes is reduced.
Humans and loons
Though mercury is a concern for local loons, both Meyer and Piper cite human disturbance as the biggest threat.
“Fishing exacts a huge cost to loons,” Piper said. Loons get tangled in monofilament line and swallow lead tackle. Piper says that two to three loons in his study area are killed each year by fishing encounters, a loss that he calls “not trivial.” Exchanging lead for alternatives is one way to protect loons and other wildlife.
Loons are also particularly vulnerable while they are nesting. Piper and Meyer suggest learning where loons nest and ensuring that boats, children, and pets stay away from the area during May and June.
Though accidents do happen, local residents tend to be protective of loons and supportive of the research. More than 50 citizen scientists assist Meyer’s research by collecting data through the Loon Ranger program with Loon Watch. Many households also allow researchers to access private lakes through their property. Piper said, “The kindness and generosity of lake residents have made the study possible.”
The local appreciation of loons, paired with the findings of Piper’s and Meyer’s research, seems to indicate a strong future for loons in northern Wisconsin. Similar to other fish-eating water birds, the population of loons in Wisconsin was lower in the 1960s and 70s, most likely due to botulism and red-tide die-offs, illegal shooting, and DDT. Over the past three decades loons have returned in presence and adoration.
“The loon is emblematic of the wild north,” Meyer said. “The public is very engaged and supportive of loon conservation.”