The moon over Lower Hay Lake set just before midnight, adding welcome darkness for a team of researchers on a mission to capture loons.
From the rear of their meandering skiff, a crew member sounded a device that mimicked a crying baby loon. The wail echoed into the night with no response.
Up front, wildlife biologist Kevin Kenow raked a spotlight across the black water. Hours passed. If the strategy worked, an adult loon would answer the distress call and swim blindly into the beam. Kenow would then net the animal for tagging and sampling.
“Birds are tough tonight,” he whispered to everyone on board.
Minnesota’s beloved loon population — the largest in the U.S. — is stable at about 12,000 breeding adults. But wildlife officials see a rising threat to vital nesting areas from relentless lakeshore development across the state that can pollute water, erase wild shorelines necessary for chick rearing and invite raccoons and other critters that attack nests.
Loons stopped reproducing on lakes when shoreline development exceeded 25 buildings per kilometer, or about six-tenths of a mile, a study in Wisconsin has found.
Kenow and other wildlife researchers are concerned about safeguarding special feeding areas — specifically deep water lakes where loons apparently congregate to fatten up on highly nutritious ciscoes, a type of whitefish that is a staple of another Minnesota cold-water inhabitant, the lake trout. There are about 650 cisco lakes in Minnesota and proof of their importance to loons could elevate them as candidates for restoration and preservation. It’s the kind of research that will shape a new era of loon conservation in the state, and it will be funded by the $18 billion BP oil spill settlement fund.
Carrol Henderson, nongame wildlife leader for the Minnesota Department of Natural Resources (DNR), was notified just last week that millions of BP settlement dollars for loon restoration could start arriving here by midsummer 2017. About 85 percent of Minnesota loons winter in the Gulf of Mexico and were among the many wildlife species contaminated by the massive 2010 petroleum disaster.
The state’s share of the global settlement money is projected to be in the range of $5 million to $10 million, far less than originally thought, Henderson said. But it will stretch out over 15 years and DNR officials want to steer much of it into permanent land easements that preserve forests, wetlands and other natural landscapes around key lakes.
Smaller allotments of oil spill money are slated for restoration of degraded habitat, construction of loon nesting platforms and abatement of lead fishing jigs and sinkers, which fatally poison some loons every year.
“There’s a whole new level of technology giving us more insight into loons,” Henderson said. “The research is really advancing our understanding … by light-years.”
Kenow, a loon expert for the U.S. Geological Survey (USGS), proved previously with pressure-sensing leg bands that Minnesota loons that visit Lake Michigan during annual migrations to the Gulf dive 140 feet deep. There, they forage on bottom-dwelling bait fish as part of their fall migration. Their dives last as long as 2.5 minutes and their subsequent flights to the Gulf have been clocked at 70 mph, fast enough for nonstop trips when aided by good weather.
Over the past three months, Kenow’s crew in Minnesota has been attaching similar leg bands to loons on Lower Hay, Lower Whitefish and other deep lakes in the Whitefish chain.
They have captured and recaptured birds from at least 24 different loon territories in the area and are waiting for analysis of fecal swabs, blood draws and DNA sampling. From recaptured loons, they’re downloading location data archived in the leg bands. The mosaic of information should describe how deep the loons are feeding and precisely to what degree they’re nourished by ciscoes, also known as tullibees.
“I’m thinking along the lines of being able to demonstrate the importance of cold water cisco lakes to common loons,” said Kenow, a University of Minnesota graduate who is based in La Crosse, Wis.
Oily, high-calorie ciscoes live in the coldest portions of deep lakes, where oxygen levels are locked in for long periods. Lake biologists worry that runoff from increasingly developed watersheds will cause unwanted weed and algae growth. When the excess plants die, they drop to the lake bottom and soak up dissolved oxygen vital to the survival of ciscoes.
Kenow said fall sightings of loons flocking to the surface of deep lakes around the state provided impetus for his latest research, aided by the DNR. Demonstrating the importance of individual deep lakes to loons, the researchers last year documented aggregations of 100 loons on Lower Whitefish and 40 loons on Lower Hay. Big Trout, another deep lake in the Whitefish chain, also attracted crowds of loons, Kenow said.
Unraveling loon mysteries
Kenow has studied loons, a federally managed natural resource, since 1996 and currently spends a quarter of his time on the charismatic birds. His migration studies found that Minnesota’s loon chicks fly south all on their own, departing after their parents and reaching the Gulf unassisted. They winter closer to shore than the adults.
Leg banding has shown that juveniles don’t return to waters near their birth until their third, fourth or fifth spring. Instead, they migrate up the East Coast or into the interior of Canada. Satellite telemetry and other tracking studies have revealed half of these developing loons die from accidents, avian botulism, red tide algal blooms, motor boat props and other causes.
Though the common loon is among the most studied bird species in the world, researchers in Minnesota and Wisconsin are still unraveling new mysteries, including the myth-buster that loons — in fact — don’t mate for life.
Chapman University Prof. Walter Piper, who is funded by the National Science Foundation to study territorial loon behavior in northern Wisconsin, said in an interview that a typical loon will have multiple mates during its lifetime. The reason? Loons live into their 20s and early 30s and mating pairs can be split during fights with other loons competing for prime territory. Piper and Kenow both said males have shorter life spans and commonly die in eviction fights. But males and females alike can be ousted from a given territory. Piper said one banded female loon in his study has gone through at least five younger mates during 20 years of breeding.
Loons are genetically wired to return to the general area of their birth, or natal lakes. They also tend to choose a lake with similar biology as the one where they were hatched. That’s true even if their natal lake was crummy by loon standards, Kenow and Piper said.
In the aftermath of the BP oil spill, Minnesota was quick to provide federal wildlife authorities with significant information about loons, Kenow said. Early research showed that a number of loons found dead after the spill had picked up carcinogens that come from petroleum.
Henderson said the DNR has been using state lottery proceeds to monitor the health of loons and pelicans in the wake of the oil spill. In the future, he said, payment for those efforts might come from a separate “monitoring fund” in the BP settlement account.
Kenow said loons captured at night for his cisco-eating research have been difficult to recapture this summer because they don’t fool easily the second time. But when he was skunked on his recent outing on Lower Hay Lake, he immediately relaunched on nearby Bertha Lake to take advantage of the good weather and his crew’s availability. Bertha wasn’t a cisco lake, but it offered a chance to band new loons for general study.
As Kenow and the DNR’s Lori Naumann spied the water with hand-held spotlights, USGS researcher Steve Houdek motored the skiff to a dark cove about 2 a.m. There, a loon surfaced 100 feet away — one eye glinting in a beacon of light. Kenow whistled and hooted in hushed tones. The targeted loon, a big male, yodeled and stayed put. He then swam directly toward the boat as Houdek sounded the baby-in-distress call. Kenow netted the animal and shifted it by hand to a plastic holding crate aboard the boat.
In the same manner, the crew quickly caught the big loon’s chick. On a nearby dock, the researchers took measurements, blood samples, fecal samples and one wing feather from each bird. The chick, just nine weeks old, already weighed seven pounds. The two loons were marked with uniquely colored leg bands and then returned to the cove where they were captured. It was nearly 4 a.m. and the crew was planning a return to Lower Hay in 16 hours for another round of “nightlighting.”