Holderness, New Hampshire – Tiffany Grade sweeps her binoculars over tangled tree roots at water’s edge. She spots a black and white checkerboard of feathers in a lichen-covered crease in the shoreline – a loon sitting on a nest. Just offshore, a second loon glides past, dives, then disappears.
To the untrained eye, it’s an idyllic summer scene on Squam Lake. But to a loon biologist like Grade, it’s trouble.
“Do you see the way he stretches his neck up?” Grade says, pointing to the diving bird. “He knows he’s some place he shouldn’t be.”
The male intruder is biding his time until the nesting loon leaves. This vying for territory imperils the unhatched chick: Its parents can be killed or distracted, leaving the egg undefended or the chick unfed. And if one parent is ousted, the intruder kills the chick.
At Squam Lake, it’s social chaos. Chicks are dying. Eggs aren’t hatching.
It’s a scenario playing out across North America – loons are raising fewer chicks to fledgling stage than they were two decades ago.
Researchers suspect that hormone-disrupting pollutants such as flame retardants may have eroded the birds’ delicate social structure and contributed to a mysterious drop in Squam Lake’s loon population. In other parts of the Northeast, scientists have implicated acid rain and mercury in declining numbers of chicks. Loons with high mercury levels lay and hatch fewer eggs, and they’re not good parents.
Once facing steep declines in much of their U.S. range, loons have made a comeback in the last 40 years. Now this success story is in jeopardy.
Often referred to as the “spirit of the North,” the common loon, with its piercing, plaintive wail and beady red eyes, has long been a cultural icon across the Northern United States and Canada. Its profile adorns the Canadian dollar, and license plates from Maine to Montana. Enormous fiberglass loons stand sentinel over small towns in Wisconsin and Minnesota. The bird features prominently in many Native American legends, including the Ojibwe creation story. Even Thoreau described the loon’s “unearthly howl, probably more like that of a wolf than any bird,” as the “wildest sound” ever heard at Walden Pond, “making the woods ring far and wide.”
Many credit the return of the loon’s irreverent echo to a conservation initiative spurred by Squam Lake residents in the 1970s.
In New Hampshire, the number of breeding pairs has more than doubled from 87 in 1980. Today, the BioDiversity Research Institute – a Maine-based non-profit focused on loon conservation and research – calls the loon population “relatively healthy” with estimates of more than 250,000 breeding pairs throughout the northern U.S. and Canada.
Quebec and Ontario are host to more than half of North America’s breeding loons, with nearly 100,000 mated pairs in Ontario alone. While the loon’s range appears to be expanding in parts of the Northeast and Midwest, in states such as New Hampshire, Vermont and Wisconsin, the number always has been more modest.
“The focus isn’t to save the species, it’s to maintain the species along the southern periphery of its range,” said Joe Kaplan, director of Common Coast Research and Conservation in Michigan’s Upper Peninsula.
In the 1970s, striking declines were observed throughout large parts of their historic range, which once extended into Pennsylvania and southern New York in the East, Illinois and Indiana in the Midwest and into Northern California on the West Coast. Lakeshore development, an increase in predators such as raccoons and coyotes, sport shooting and pollution may have factored into the declines. Alarmed by the prospect of losing the loons on Squam Lake where he summered, retired New Hampshire businessman Rawson Wood founded the Loon Preservation Committee in 1975. His efforts spawned a series of conservation programs across the country.
“There was really very little information on the basic nesting ecology of loons at the time,” said Scott Sutcliffe, former director of the Loon Preservation Committee.
Early on, the conservationists began deploying nest rafts – tiny artificial islands – to lessen the pressures of predation, human disturbance and water level fluctuations, which threaten their nests on land.
Loons nest near shoreline – usually within a foot or two of the water, often on small islands. The placement of their legs – far back on their bodies for a streamlined underwater shape – leaves them graceless on land.
“Watching them go that short distance to the nest, you’d think they were trying to climb Mt. Everest,” said Grade, a biologist with the committee.
The rafts were a success. Hatching rates have since increased by up to 119 percent on some lakes.
The rafts “were a visible symbol for locals to rally around,” said Jeff Fair, former director of the New Hampshire Loon Recovery Project.
A lot of what was learned about loons’ reproduction came from watching them at Squam Lake.
“The loons here may be some of the most intensively monitored anywhere,” said Harry Vogel, director of the Loon Preservation Committee. That’s what made a mysterious population crash in Squam’s loons so unsettling.
“If it can happen here, under such careful watch, it can happen anywhere,” he said.
The trouble on Squam started in 2004. Between the fall of that year and spring 2005, Squam lost seven of its loon pairs – a decline representing 44 percent of the lake’s population. It was a “catastrophic event,” said Vogel, a drop unprecedented in 39 years of monitoring loons throughout the state.
In the years before that, Squam’s loons were flourishing. In 2003, 16 breeding pairs produced a record 15 surviving chicks. Typically, the population is considered viable if one chick survives every year for every two breeding pairs.
Between late September and early November each year, Squam’s loons take flight – migrating to separate spots off the Atlantic coastline from Maine to Rhode Island. Several of Squam’s loons never returned from the wintering grounds and the banded birds were never seen again.
They likely died during the winter while they were on the ocean.
Concern deepened in 2007 when the remaining loons experienced almost complete reproductive failure. Of the three chicks hatched on Squam that summer, only one survived to fledge.
“It was the worst year since 1978,” the year they were listed as a threatened species in New Hampshire, Vogel said.
Vogel, Grade and others collected the eggs that didn’t hatch. Chemical tests revealed high levels of several contaminants, including brominated flame-retardants, a perfluorinated chemical formerly used in Scotchgard, polychlorinated biphenyls (PCBs) and chlordane, a pesticide banned more than 20 years ago. The levels were up to nine times higher than those measured in abandoned loon eggs collected from Maine, New York and other New Hampshire lakes. Higher levels of contaminants in eggs collected from the northeastern section of the lake and high levels of flame retardants in crayfish from tributaries flowing there suggest a possible pathway for contaminants. But the sources are unknown.
In humans and lab animals, the chemicals found in Squam’s eggs are suspected of disrupting hormones and could impair reproduction, the nervous system or the immune system. Little, however, is known about the effects on loons.
Vogel hypothesizes that contaminants may have played a role in the initial population decline on Squam. Fall is a stressful time for loons: They molt and grow new feathers, then migrate to the coast, where they transition from a freshwater to a saltwater ecosystem. These processes are energetically costly, so loons dip into their fat stores, which could release contaminants that build up in fat, leaving their health compromised just as they reach the ocean.
“We’re closing in on a possible cause for the collapse, but without recovering the loons that were lost, we’ll never know for sure,” Vogel said.
Grade steers the boat into a large cove – and another loon pair’s territory. The pair successfully hatched two chicks from a nest raft earlier in the summer.
Loons are true water birds. Within several hours of birth, the family leaves the nest. The chicks – carried on a parent’s back at first – spend most of the next four to five years living almost exclusively on the water, much of it on the ocean – until they return to the breeding grounds to establish their own territories for nesting.
Three times each week, Grade checks on loon families by patrolling their nesting territories, which can be up to 300 acres each.
The moments before she spots new chicks through her binoculars – the brown puffballs bobbing on the water’s surface – have become the most stressful part of her week. Last year was a bad one: Of the 12 pairs of loons that nested on Squam, only two chicks hatched and only one survived.
Grade calls it “social chaos” – the unraveling of the loons’ social structure when new loons compete for territories.
The adult population on Squam appears to have rebounded from the 2005 low of nine breeding pairs with several “single” loons occupying common areas – largely immigrating from surrounding lakes. But turnover is high. Deaths of adult loons are on the rise. And the majority of deaths, it seems, are due to human causes.
Since 2001 – the same year a new public boat launch opened – lead poisoning of loons on Squam Lake from ingested lead fishing tackle has more than doubled to twice the statewide average. Of 11 birds found dead between 2004 and 2013, five had lead tackle in their gut. Statewide, lead poisoning deaths in loons decreased over the same time.
With naturally low reproductive rates and a long life span (they can live up to 30 years or more in the wild), loons thrive in a stable environment with a steady social structure. It takes time for a new pair to establish itself in a territory after the loss of a mated adult. A decline in reproductive success often is the result.
“There’s been more loon fights in the years since the initial decline than in all the previous years of monitoring combined,” Grade said.
The territorial takeovers tend to be low-key, she explained. “Most people won’t even know there’s a fight going down.” There’s a lot of posturing and “penguin dancing” – where they’ll rear up, wings spread, and rapidly beat their feet against the water. Sometimes it gets physical: One bird may peck another bird, hold its head underwater or even spear an opponent’s belly from underneath. The consequences of a “smack down” may be severe, with death or injury to one or both birds.
“Loons really are a species on the edge,” Vogel said. “We’re learning from Squam that the fallout from a single event can last a decade or more,” he said.
More than a hundred miles south of Squam Lake, Lee Attix pokes at eggshell fragments concealed by ferns and swamp grasses at an abandoned raft nest on the Quabbin Reservoir in central Massachusetts – one of the most southerly breeding lakes for North America’s loons.
Attix is surveying the reservoir’s 19 known breeding territories for chicks. Before they fledge in the fall, the researchers will return to band the new birds, draw blood and take feather samples from adults and juveniles.
“Massachusetts is a priority for us,” said Attix of the Biodiversity Research Institute.
Last year, the Maine-based nonprofit launched a long-term, multistate research initiative to identify stressors to loons in states including Massachusetts, Minnesota and Wyoming with the hopes of increasing their reproductive success along the southern edge of the current range.
Missing from Massachusetts for nearly a century, the first pair of breeding loons returned to the state in 1975, nesting at the Quabbin. The reservoir created by the inundation of a valley and four towns in the 1940s to meet Boston’s growing water demand hadn’t even existed the last time loons had nested in the state.
In 2012, 35 loon pairs bred in the state, a five-fold increase since 1985. But reproductive success remains low here, too. In only four of the last 15 years did loon populations meet the sustainable level of 0.48 chicks per pair.
“We tend to start off with strong nesting numbers in the spring, but by the end of the season, there’s relatively little productivity,” said Dan Clark, Director of Natural Resources for the Massachusetts Department of Conservation and Recreation.
There is reason for hope. This breeding season has been a favorable one for the Quabbin Reservoir’s loons. Nine of the 19 breeding pairs have successfully hatched chicks this season, according to Clark. “Typically we might see two to three pair,” he said.
Two Old Villains
An old villain in these waters may have returned to harm these loons. The scourge of the 1970s and 1980s, acid rain decimated many freshwater lakes, particularly in the Northeast. Sulfur and nitrogen emissions from power plants and other sources reacted in the atmosphere, creating acids that blew great distances. Falling as rain, snow or dust, the acids lowered the pH of lakes, killing fish and disrupting entire ecosystems.
While sulfur emissions have decreased in recent decades, levels in some lakes – especially in eastern Canada and the U.S. Northeast –remain high.
Last year, the Canadian Lakes Loon Survey, a 32-year study, identified acid rain and mercury as the primary contributors to drops in the reproductive success of loons across Canada over the last two decades. On lakes with high mercury levels, researchers found a 50 percent drop in the number of chicks per pair. The report concluded that annual reproductive success across Canada could drop below the minimum required to maintain a stable population around 2016.
In addition to increasing the bioavailability of mercury, acidity can mess with fish reproduction and survival, making the loons’ primary food source scarcer in acidic lakes. When a lake’s acidity increases, conditions become more favorable for mercury particles to be taken up into the food chain. Sulfur, a strong acid, feeds bacteria in lake bottom sediments that alter the chemistry of the toxic metal, making it more available for uptake by plants and animals. Once in the food web, mercury accumulates at higher and higher levels, as one animal eats another. Loons are at the top of that web, so they build up some of the highest levels.
In Massachusetts, estimates suggest mercury exposure may account for a 23 percent drop in loons’ reproductive success.
To many birds, mercury is a highly potent neurotoxicant; it can alter the nervous system and damage developing embryos.
The effects of mercury on parental care are subtle, but they can have a big impact on whether chicks survive, said Dr. Nina Schoch, director of the Adirondack Center for Loon Conservation in New York. Loons exposed to mercury are a little more lethargic, a little more inattentive.
“They don’t forage for fish or defend their territories as well,” Schoch said. They spend less time on the nest than birds that are behaving normally, which leaves the eggs vulnerable to predation or changes in temperature.
In a few weeks, loons on the Quabbin Reservoir, like their counterparts on lakes from British Columbia to Minnesota and Maine, will begin to shed their glossy plumage for a muted winter palette. They’ll migrate to the Pacific, the Gulf Coast or the Atlantic Seaboard. Chicks will stay behind on their natal lakes slightly longer, growing their first set of flight feathers and gaining strength.
On their journeys, loons face even more threats. Marine oil spills are of particular concern. And in recent years, avian botulism outbreaks on the Great Lakes have felled thousands of loons stopping over on fall migration.
“Botulism has the potential to rewrite the story for loons,” Kaplan said.
Yet year after year, most loons do make it back to their breeding lakes to try again. The tradeoff for low reproductive success is a long lifespan. “If they nest year after year for decades their chance of replacing themselves in the population is pretty good,” Fair said.
It’s a delicate balance that has worked well for millennia, but a fragile one enmeshed with human activities.
“We have the potential to hurt,” Grade said, “and the potential to help.”