The haunting, echoing call of a loon is a hallmark of Wisconsin’s Northwoods.

So, too, is seeing the regal bird floating along a lake’s surface, sometimes with a small, fluffy brown chick on its back.

But when Elaina Lomery visited a lake in Oneida County to check on a chick a fellow researcher had documented 10 days earlier, she noticed something strange about the little bird. It had some yellow fluff instead of a full brown coat. Lomery, who has documented lots of loon chicks, realized it wasn't a chick at all. It was a duckling — a mallard.

But the little duckling was still cruising around with a breeding pair of loons like it was their chick. The duckling rode on the female’s back. It dove deep underwater to find food. Its adoptive parents guarded it closely and scanned the skies and water for predators like eagles and muskies. It was a regular Northwoods version of “Babe,” the movie about the pig that thought it was a border collie.

The unlikely foster family was documented by the Loon Project, which since 1993 has studied common loons and their territorial behavior in northern Wisconsin. And it wasn’t the only unusual thing the project observed this year.

Loon love

The Loon Project is directed by Walter Piper of Chapman University in Orange, Calif. A Cleveland, Ohio, native, he became interested in loon behavior while working on a postdoctoral project on white-throated sparrows in Michigan’s Upper Peninsula in 1992. He was staying at the Whitefish Point Bird Observatory, which was run by Dave Evers, who had developed an efficient way for catching and banding loons.

Evers was mostly interested in methylmercury in loons, but in the course of their studies, they noticed loons were exhibiting a unique territorial behavior. One would kick another off a lake, and the evicted loon would move to a nearby lake. That kind of eviction behavior is not well documented in any animals, Piper said, so he decided to pursue studying it and launched the Loon Project the following year.

For six weeks every summer, Piper heads to northern Wisconsin to band and track loons, this year on 120 lakes. Research assistants — often college students or recent graduates like Lomery, who is working with the project for a second summer — assist in documenting the loons.

Since its founding, the project has banded adults and chicks on 200 lakes in northern Wisconsin, followed 65 loons through their entire breeding lives and watched 427 of its banded chicks grow into adults.

Through that research, Piper has dispelled one of the most common myths about loons, that they mate for life. They can live for more than 20 years (and one has been documented to be older than 30), and in that time they exhibit some of that territorial behavior. If one is evicted from a lake, its mate does not follow. Both might find new mates.

Loons do, however, adopt loon chicks, Piper said.

Animal rehabbers who rescue orphaned or injured chicks will reintroduce them to a loon family that has only one chick.

“They don’t discriminate much between loon chicks,” Piper said.

Unlikely family

But in 27 years of collecting data on loons in northern Wisconsin, the mallard-loon adoption was a first.

Piper blogs about the project’s findings on its website, loonproject.org. He first wrote about the “Unlikely Allies” on June 29, after Lomery confirmed it was a duckling. Piper speculated the loon parents had hatched a chick, but it had not survived. Around the same time, he figured the duckling had somehow been separated from its mother and siblings.

But the question remained as to why the loons had adopted the little duckling.

“Loon pairs provide extensive parental care for their young, of course, and are hormonally primed to do so,” he wrote. “In any event, the tiny waif was likely discovered by the loon pair just after they had lost their chick and were predisposed to find and care for anything that even remotely resembled a newly hatched loon.”

Piper said there have been cases of loons adopting ducks before. A pair of Arctic loons cared for an eider duck in the '70s, and a few years ago Piper reported on a couple common loons in British Columbia that adopted a goldeneye.

But both of those were diving ducks, which dive underwater for food like loons. Mallards are dabbling ducks. They like to hang out along shore and dunk their heads underwater to feed on invertebrates and plants in shallow water. They don't eat fish, like loons do.

At first, the Loon Project observed the duckling refusing the fishy food. But by July 9, Piper wrote the duckling was accepting small pieces of fish from its adoptive parents, plus snacking on plants like lily pads on its own.

Linda Grenzer, a naturalist and photographer, also captured images of the duckling diving deep underwater like its loon parents.

On July 15, Piper wrote that “the loon pair and mallard duckling remain a close-knit family,” and by July 23 he said the mallard was thriving and nearly full-grown, living on fish from the loons.

But some species differences were becoming more evident.

Whenever one of the loons would surface with a fish, the eager duck would rush across the water to get it. Loon chicks are usually more lackadaisical about getting to the dinner table.

“It’s kind of a funny thing to see,” Piper said. Not just the scramble, but the overall spectacle of a mallard duckling being fed by a male and female loon. Mallard females do not directly feed their ducklings, and males are not involved in rearing at all.

“This is a completely novel experience that this mallard duck is having, and who would know that it would be able to adapt to getting food by grabbing it out of the bill of its parents, and for that matter, standing on the back of its parents,” Piper said.

Piper also blogged about another observed behavior that separated the mallard from a loon.

In July and August, “single loons search ceaselessly, and at times desperately, for territories and mates,” he wrote.

One sign of a good territory is the presence of chicks with a breeding loon pair.

To protect their territory, breeding pairs do all they can to hide their chicks from not only predators, but also other loons. If the pair spots another loon, they will dive underwater and swim to the middle of the lake while the chick dives and heads for shore to hide.

But the duckling didn’t know about this strategy. Grenzer observed the family resting when another loon appeared in the sky. The parents did what loons do and dove underwater to engage the invader in the middle of the lake. The duckling did not do what chicks do, however.

“Instead of diving itself and racing underwater to hide near shore, as a loon chick would have, the duckling freaked,” Piper wrote. “When it spotted its foster parents far away and next to non-breeders that had landed, the duckling raced towards middle of the lake, while peeping loudly, making itself very obvious.”

While the unwelcome visitors probably would not confuse a duckling for a loon chick, they might still have taken notice of the “protective and aggressive behavior exhibited by loon parents,” Piper wrote, putting the breeding pair’s territory in jeopardy next year.

For now, the pair and its Babe remain safe. Piper and his team will continue to observe the family, and he’s curious to see what the duck does when it's fledged.

“My guess is that it would find other mallards and start to hang out with them, but it’s not certain,” he said.

While the duck has thoroughly imprinted on the loons, he said, “mallards and loons are not friends. They’re very different and don’t cross paths that much.” He noted loons often give mallards a hard time, and have even been known to kill ducklings.

“To have loons adopt and care so much for this duckling is touching and poignant and bizarre,” Piper said.

Three’s company

It’s not the only poignant and bizarre moment from the project’s observations this summer, which Piper said has been “really tough” in general, with fewer chicks.

One bright spot is a pair of loons that hatched three chicks, which Grenzer captured in a photo that shows the smallest chick on top of one of its siblings, which in turn is perched on its parent, while the final sibling trails behind. Piper dubbed it a "a loon pyramid.”

The three chicks are a rarity that Piper has only seen once before, and in that case only one of the chicks reached fledging age. He wrote that case makes him nervous about these triplets.

“My scientist’s sense tells me that the gamma chick is doomed, and the beta chick’s survival is highly uncertain,” he wrote.

“There’s a lot of luck involved. It’s hard to take care of two chicks,” he said, noting the difficulties the adults have in wrangling their young and protecting them from eagles and other loons.

But at nearly three weeks old, the trio has already lived longer than the two that did not survive before — a source of hope in what “has been a dismal year for loon breeding in northern Wisconsin,” Piper wrote. He noted that only a quarter of their lakes produced young this year, while over half did last year. He thinks a late ice-out that led to a bad, prolonged bout of black flies probably chased loons off their nests, leaving their eggs vulnerable to predators.

While Piper cautioned against drawing any conclusions about the loon population from one year of data, especially considering a 2008 study that showed the loon population in Wisconsin was stable overall, he has recently observed a concerning trend of reduced reproductive success.

The rate of chick production per territory in Piper's study area has fallen. To put it simply, fewer pairs are producing two chicks, he said.

“That’s a worrisome pattern that we just recently have noted and are trying to make sense of,” he said.

He added that another researcher thinks catch-and-release fishing practices might factor in to the decline. When fishermen release big game fish like musky and largemouth bass back into lakes, those fish compete with loons for the same food sources, panfish like crappies and bluegills. Humans are also angling for those panfish, further depleting the loons' food source.

And in addition to other natural and anthropogenic threats — from motorized boats to lead fishing equipment — loons in Wisconsin also are facing the looming threat of climate change.

According to the Climate Report produced by the National Audubon Society in 2014, Wisconsin's loon population is projected to be gone by 2080, having moved north. Overall, common loons are forecast to lose 56% of their summer range and 75% of their winter range by then.

“That’s a real wake-up call,” Piper said, but “it’s good to view that with a degree of skepticism.”

"Their projection is likely to provide a crude estimate of the impact of climate change on loons, not a precise one,” he wrote on his blog. “That is, loons are likely to cope with climate change better than most other birds — as they have other environmental threats. Then again, loons might be especially sensitive to climate change and retreat northward more rapidly than the study predicts.”

For now, Piper will continue to watch his loons in a pocket of northern Wisconsin, cheering for the family of five, marveling at the mallard who is in the midst of a nature vs. nurture struggle.

And as the ice starts to creep across lakes in northern Wisconsin, the haunting call of the loon will disappear until next spring, when the loons will be back to do it all over again.

Contact Chelsey Lewis at (414) 224-2144 or clewis@journalsentinel.com. Follow her on Twitter at @chelseylew and @TravelMJS and Facebook at Journal Sentinel Travel.