Sounds Like Home: Experimenting with Audio to Help Marbled Murrelets Find Prime Habitat

Endangered Marbled Murrelets are the latest in a line of species to show promising results from a conservation technique called social attraction.

From the Spring 2022 issue of Living Bird magazine. Subscribe now.

The email invitation from the team at the Oregon State University Forest Animal Ecology Lab prom­ised an easy excursion into Oregon’s coastal old-growth forest: 1.5 miles each way over “mostly flat” terrain. But like many things related to the Marbled Murrelet (Brachyramphus marmora­tus), reality wasn’t that simple.

The trek into the Siuslaw National Forest began innocently enough. I accompanied Jim Rivers, Oregon State wildlife ecology professor, and his crew to replace the batteries on a Marbled Murrelet’s nest monitor and radio telemetry system. And the terrain did prove mostly flat—except for the numerous steep ravines and drainages along the uncut trail, and the final, steep hand-over-hand scramble to get to the giant Douglas-fir that a fluffy, fist-sized murrelet chick called home.

This dense, verdant neighborhood is prime murrelet habitat, which is in short sup­ply across the murrelet’s range, where most old-growth stands of soaring Douglas-fir and Sitka spruce have been logged off.

But it turns out decent habitat is only one part of the murrelet’s equation for selecting nesting areas. They also need to know whether they can find adequate food for their chicks, and if there are dangers from predators. For that information, many murrelets turn to a trusted source: each other.

Rivers and his team tried an experiment using this peer-to-peer communication tendency among Marbled Murrelets—whose populations have cratered along with the loss of old-growth—to lure the federally endangered seabirds into habitat that was thought to be unoccupied. They used audio playbacks of murrelet breeding calls to convince other murrelets that their kind was already here. It’s a strategy scientists call social attraction, and it uses artificial social cues, such as decoys and recorded calls, to trick birds into breeding in new locations.

Social attraction was initially devel­oped for use in colonial seabirds—birds that nest in large congregations near the ocean. To date, the Seabird Restoration Database, a global project tracking out­comes of social-attraction and transloca­tion efforts in seabirds, has logged more than 800 such efforts. (See Mexico’s Conservation Efforts Spur Dramatic Recoveries for 20+ Species of Seabirds, Summer 2020]. One-third of all seabird species have benefited from social-attraction conservation projects, according to Stephen Kress, the founder of Audubon’s Project Puffin. Kress famously pioneered this method for bringing Atlantic Puffins back to Eastern Egg Rock Island off the coast of Maine in the 1970s.

Now conservationists are trying the approach with other species, including birds that live inland. Marbled Mur­relet, it seems, may be just the latest in a growing list of birds that can be successfully tricked by social-attraction techniques, for their own good.

Hidden Secrets of Nesting Biology

The Siuslaw National Forest, where Riv­ers went bushwhacking, is near the southern end of the Marbled Murrelet’s breeding range. In the 1790s, the British Royal Navy crew of the HMS Discovery—Captain George Vancouver’s ship that explored the west coast of North America—found the wa­ters off the Pacific Northwest filled with murrelets and their ghostly keer, keer cries as the plump birds lifted off, flew inland, and disappeared into the fog. Over the next 200 years, not much more was known about where murrelets go.

Then in 1974 a tree trimmer in cen­tral California found a khaki-colored, web-footed fluffball nestled on one of the mossy branches of a Douglas-fir that needed to come down. While out on a routine trim at Big Basin Redwoods State Park in the Santa Cruz Mountains, Hoyt Foster was 147 feet off the ground when he came face to face with a beige chick that he said looked like “a porcupine with a beak sticking out.” The bird was safely ensconced in a soft, mossy bowl excavated on the branch itself. A tree surgeon and avid birder, Foster noticed the bird’s webbed feet and brought the chick to a nearby wildlife rescue center. Scientists were finally clued in to the nesting habitats of a portly little seabird that prefers the tops of massive, old-growth trees.

Even in a good year, a pair of murrelets may only produce a single chick, which makes the availability of breeding habitat crucial to their sur­vival. Marbled Murrelets use the broad, mossy limbs of ancient fir, spruce, and hemlock for nesting. But rather than building a nest per se, murrelet parents scrape away some of the moss to create a bowl-shaped depression that will keep the green-spotted egg and resulting chick from rolling off.

Ornithologist Kim Nelson’s lifelong obsession with the Marbled Murrelet began in the 1970s, not long after the dis­covery of their treetop nesting sites. But while biologists had discovered where murrelets nest by dumb luck, Nelson soon found that further study of the birds would take more effort. The now-retired Oregon State professor began a decades-long habit of rising at 2 or 3 a.m. from May to September for a dawn stakeout of stands of towering trees that might hold murrelet nests. The dense canopy, dark skies, and sheer speed of murrelets on the wing (murrelets zoom in from the coast at 60 to 70 miles per hour) meant that Nelson and her team might only have a split second to spot a bird before it disappeared overhead. The next day, they moved 25 to 50 meters from their first spot in the direction that the bird was headed and tried again. The work was frustratingly slow. In four years, her team located just 10 nests.

“Even with five people standing in a forest near a known nest, the bird can go in and out without anybody seeing it,” Nelson says. “We found out very little on a year-to-year basis, and we always ended up with more questions than answers.”

Over time, though, Nelson’s team began to identify stands of forests where the murrelets frequently nested, and stands where they didn’t. The hard-won information that Nelson gleaned from those early studies began to fill in the blanks about the nesting habits of what nature writer Maria Mudd Ruth calls “a chunky baked potato of a bird.” Both parents take turns incubating the egg for 24 hours before swapping places and returning to the ocean to feed. They continue this pattern for the first few days after the chick hatches, and then both parents return to the ocean to search for anchovy, herring, and sardines full-time, returning only to supply the chick with regular meals. The chick’s drab feathers conceal it from predators, but the camouflage often doesn’t work—Marbled Murrelet nest failure rates average around 70%. About 90% of the failures are the result of predators such as Common Ravens and Steller’s Jays.

One of Rivers’s nest cameras caught such nest predation in the act. Up until the last second, the diminutive murrelet parent (“the size of a robin on steroids,” according to Rivers) defended the nest from the much bigger raven. “Then, just like that,” Rivers snaps his fingers, “the chick was gone.”

In the 1990s, systematic popula­tion studies of Marbled Murrelets in Oregon showed a steep decline from 9,750 murrelets in 1992–93 to 4,100 in 1997–1999. Researchers think the drop may have been a result of heavy logging in the 1980s, but because murrelets tend to live 10 to 15 years, the decline only showed up a decade later. Nelson says Marbled Murrelet numbers proba­bly started their decline much earlier in the early 1900s as a result of wide-scale logging. In the days before the arrival of lumberjacks, the sodden tract of land that stretched from Northern California up through Oregon, Washington, Brit­ish Columbia, and southeastern Alaska provided an embarrassment of coastal old-growth riches. These same trees, however, were valuable to Big Timber, which clear-cut around 80% of Oregon’s ancient stands in the 20th century.

In 1992, the U.S. Fish and Wildlife Service listed the Marbled Murrelet as threatened under the Endangered Species Act due to loss of habitat. The Northwest Forest Plan—a U.S. Forest Service agreement in 1994 that cur­tailed logging on federal lands within the range of Northern Spotted Owl—also helped the Marbled Murrelet. The population in Oregon is currently esti­mated to be around 11,000 murrelets. But the situation is far from settled. USFS biologist Martin Raphael says murrelet numbers in Oregon appear to be supported by birds moving in from other areas, but within the state repro­duction is not sufficient to support a stable murrelet population.

“There aren’t enough young being produced to replace the population of adults that are dying,” says Raphael.

The murrelet’s tenuous numbers and the paucity of data about even basic aspects of its life history led to the founding of the Marbled Murrelet Project at Oregon State University in 2015. Rivers, a forest ecologist with a love of ornithology, led the project, and Nelson was a coprincipal investigator. The goal was to figure out what kind of habitat the Marbled Murrelet needed so that scientists and land managers could make better conservation decisions.

“With more than half a million acres of [potential] habitat, we just don’t have enough information to manage the birds in Oregon right now,” Rivers says.

The specific combination of needs for the Marbled Murrelet’s nest—Methuselah-like trees with wide, flat limbs that are close to the coast, but not too close; accessible, but concealed—makes these endangered alcids rather picky when it comes to real estate. Adding to the problem was the Marbled Murrelet’s dwindling numbers, which meant they did not make for a plentiful study subject. Nor did scientists know how murrelets decided where to build their nests—key information needed to protect habitat.

Other alcids, such as auks and puffins, regard the presence of others of their species as a sign of a good place to nest, which made Nelson wonder whether murrelets might use similar cues. Granted, most alcids are highly social, breeding in large colonies, whereas mur­relets are a bit solitary. But Nelson noted that Marbled Murrelets don’t appear to be overly territorial. If a Marbled Mur­relet isn’t getting positive social cues in a given area, Nelson figured, then the bird won’t nest there—creating a negative feedback loop that could end with the extirpation of the species in Oregon.

Instead, the Marbled Murrelet Project scientists decided to try and trick murrelets into thinking that unoc­cupied patches of unlogged old-growth were already in use by other murrelets, hopefully convincing more birds to come and build nests. Rivers and Nel­son relied on a small but growing body of literature showing the efficacy of such trickery in reestablishing nesting bird populations.

An Idea as Old as Duck Hunting

In some ways, social attraction isn’t a new idea at all. Waterfowl hunters have used wooden decoys and duck calls for centuries to lure birds within range of their shotguns.

In the 1970s, ornithologist Stephen Kress was trying to lure Atlantic Puffins to Eastern Egg Rock Island to help the species make a comeback. Before being nearly exterminated in the 19th cen­tury from hunting for their meat and feathers, puffins nested on many of the rocky crags that dot the Maine coast. In the 20th century puffins enjoyed pro­tections thanks to the Migratory Bird Treaty Act, and Kress saw no reason the clown-faced seabirds couldn’t return to their former nesting grounds. He began by hand-rearing some puffins imported from Newfoundland. But getting a few puffins to Egg Rock was only part of the problem. What Kress needed to do was convince the chicks to come back as adults, after three or four years at sea as juveniles, and build their own nests there. Then he remembered duck hunters and their decoys.

Whether used by hunters or conser­vationists, the creation of avian deep­fakes to lure birds to a specific location is a strategy that builds on an animal’s innate ways of sensing the world. No single bird can sense everything going on around it, so they gather information from others of their species to avoid predators, search for food, and find a place to nest. Sight and sound provide major clues, as does smell.

Michael Ward, an ecologist at the University of Illinois and an expert in restoring nesting bird populations, puts it like this: “You can create a fancy restaurant, but if no one’s in the parking lot, people think something’s wrong with it and won’t go in.”

Many Social-Attraction Projects Use Macaulay Library Audio

The audio playback efforts that successfully attracted Northern Bobwhites to new nesting sites in Illinois, and did the same for Galapagos Petrels, relied on recordings from the Cornell Lab of Ornithology’s Macaulay Library. With more than 1 million audio recordings in the archive, the Cornell Lab is often the go-to source for scientists using audio playback for bird conservation. Macaulay Library recordings of bird songs and calls have been used in social-attraction strategies for dozens of species, including Barn Swallows in Canada and Willow Flycatchers in the Sierra Nevada mountains of California. Sound recordings in the Macaulay Library have even been used to study how sounds can entice Mexican spadefoot toads into colonizing breeding ponds in Arizona.

“Audio recordings of birds and frogs and even fish have played a vital role in helping scientists understand how animals use sounds to find suitable breeding habitat,” says Mike Webster, director of the Macaulay Library. “Through these studies, we know that recordings can help some species colonize habitats that have been made suitable through restoration efforts—one step toward bringing birds back.”

—Kathi Borgmann, Macaulay Library communications coordinator

On Egg Rock, Kress put out several dozen life-sized, hand-carved wooden puffins he bought from locals—and puffins started circling the island the very next nesting season, in 1977. Several years later, Kress added a boom box that blared puffin calls. Within hours, puffins were buzzing around Egg Rock. By the mid-1980s, Kress had reestablished a healthy breeding colony of puffins on Egg Rock.

On the West Coast, USFWS biologist Mike Parker built on Kress’s success. In January 1986, the barge Apex Houston leaked 25,800 gallons of oil off the coast near San Francisco, killing an estimated 9,000 seabirds, including more than 6,000 Common Murres. Devil’s Slide Rock—a barren, forbidding shard of granite a few hundred yards off the coast—was at the epicenter of the spill. Devil’s Slide once hosted a thriving colony of Common Murres during the breeding season. Gill-net fishing that killed birds as bycatch had caused murre populations to tumble, and the oil spill was the death knell.

By 1995, a decade after the oil spill, murres still hadn’t returned. But a $6.4 million settlement included funds to restore the murres to Devil’s Slide. Parker suggested the same strategy Kress had used in Maine.

Like Kress, Parker used recordings of the murres’ harsh laughing calls, played 24/7 on a solar-powered CD player, to lure the birds back. Also like Kress, he placed over 400 decoys around the small rock. The very first year, Parker lured six breeding pairs of Common Murres back to Devil’s Slide. He continued playing the recordings for several years, but Parker says eventually he wasn’t needed anymore. The mere sights and sounds of a few murres were enough to attract more and more murres back to Devil’s Slide. Restoration of fish species and marine habitat helped seal the deal. Today, around 1,500 breeding pairs of Common Murres once again nest on Devil’s Slide Rock.

The success of social attraction in reestablishing puffins and murres in both the Atlantic and Pacific Oceans led other scientists to try the technique with several other seabirds, including Caspian and Least Terns, Laysan Albatrosses, Chinese Crested Terns, and Galapagos Petrels. The gregarious nature of many seabirds made social attraction a natural choice.

Thousands of miles from any ocean, Ward, the University of Illinois ecologist, wanted to know whether social attraction might work for land birds as well. In his home state of Illinois, North­ern Bobwhite numbers were suffering. And farther south in Texas, Black-capped Vireos were on the decline. Neither species nests in colonies like puffins or murres, but both birds had access to recently restored habitat that they weren’t using. Ward thought that social attraction might provide the necessary nudge. In the first year of his experiments with Black-capped Vireos, he managed to attract 73 breeding pairs to five different sites in Texas.

“From day one, when we started playing vocalizations of Black-capped Vireos even at sites that had never had them, birds were showing up, partic­ularly young birds,” he says. Northern Bobwhites also responded, although less strongly than the vireos, with 12 to 15 birds attracted to new nest sites.

This sterling track record of social attraction was on Nelson’s and Rivers’s minds as they tried an experiment using audio playback with Marbled Murrelets. In 2016, the Oregon murrelet team identified sections of old-growth forest that might make good homes for the tree-dwelling seabird but weren’t currently thought to be occupied. They divided the 28 sites into two groups. At 14 of the sites, they broadcast recorded murrelet calls on a custom-designed device that could both play and record sound; the other 14 sites served as controls. The next year researchers found that audio recorders at the sites where they broadcast Mar­bled Murrelet calls were 15 times more likely to detect the birds’ plaintive keer cries being uttered by actual murrelets, a marker that the stands were occupied. Nelson and Rivers were thrilled. The scientists surmised that the birds were attracted to these sites because they heard playbacks the previous year.

Murrelets Disappear, then Return

A separate study that monitored murrelet nesting in the Siuslaw National Forest produced grim results, though. In the summer of 2017, Rivers’s team couldn’t find a single murrelet nest at their Oregon study sites. It turns out the problem wasn’t in the forest, but out at sea.

Murrelets rely on an upwelling of frigid, nutrient-rich waters to the ocean’s surface for much of their food. In the summer of 2017, however, that upwelling was virtually nonexistent. Without enough food, murrelets didn’t return to nest and breed.

But a few mur­relets resumed nesting in 2019. The pandemic put murrelet monitoring plans on hold for 2020, but the follow­ing summer of 2021 was a good one for the Marbled Murrelet in Oregon.

Work began in May, when Mike Parker—the former USFWS biologist who had brought murres back to Devil’s Slide, now executive director at the California Institute for Environmental Sciences—led a group tagging Marbled Murrelets out at sea. For weeks, the group sailed out of Newport on the Oregon coast each night, battling inky black swells in a small inflatable Zodiac. Using a powerful spotlight and a long net, the team nabbed the notoriously quick, drab-colored birds and attached small radio tags.

The tags broadcast a signal to allow Rivers’s crew to find where the birds nested. Once they located a murrelet nesting tree—not a foregone conclu­sion over thousands of acres of rugged wilderness—a professional tree climber operating under a federal permit set up a camera and other recording equipment so the scientists could monitor what happened. Sometimes Oregon State fac­ulty research assistant Jon Dachenhaus had to trek in to replace the batteries on the recorders, lugging up to 50 pounds of equipment through the forest.

On the day I accompanied Dachen­haus into the Siuslaw National Forest, he shrugged off the rigor of the work. A committed bird lover, his wiry right bicep sports a tattoo of a Sandhill Crane that flexes as he drags the battery packs away from his battered white pickup truck and up the hill. Dachenhaus deftly dodges the thickets of blackberries and salal berries festooned with thorns big enough to eat his Carhartts for break­fast. Rivers accompanies him, an excuse to get out of the lab. The branches and terrain mean hard hats are a necessity.

By this time in mid-August, nearly all the surviving chicks have already fledged. But the scientists are still replac­ing the batteries on one radio transmit­ter receptor and checking on the status of a late bloomer.

The team’s two-hour trek revealed that the Marbled Murrelet chick remained safely ensconced in its mossy crib. From the ground, it was invisible. But an iPad showing a live feed from the nest cam revealed the tiny chick. In another week or two, they predicted, it would leave its nest and head out to sea for the next two years, before returning home to nest and continue the cycle.

Altogether in 2021, the team tracked 17 Marbled Murrelets back to nests in the Oregon coastal forest—more than the last three years combined. What that means for the future of murrelets in Oregon, however, remains unclear.

In the summer of 2021, the state of Oregon upped the urgency of the Marbled Murrelet’s state-listing status from threatened to endangered, which will force the state to take stronger actions to save the bird. Although the 1994 Northwest Forest Plan helped reduce the threat of old-growth timber logging, it hasn’t been eliminated com­pletely. More worrisome is the impact of climate change on northern Pacific upwelling. Oregon’s murrelets can’t take too much more of that.

Social attraction as a conservation technique, however, looks more prom­ising than ever. On Desecheo Island off Puerto Rico, a team of scientists recently used social attraction in an effort to restore nesting populations of Bridled Terns and Audubon’s Shearwaters. Last year in Maryland, conservationists built an artificial island and launched it into the Chesapeake Bay to provide additional breeding space for Royal and Common Terns and Black Skimmers, as natural barrier islands are swallowed by the rising sea. To lure the birds to the new nesting spot, Dave Brinker, an ecologist with the Maryland Depart­ment of Natural Resources, broadcast the birds’ calls from the artificial island. Within hours of beginning playbacks, terns started showing up. Twenty-three pairs of terns nested, 19 had at least one chick, and a total of 22 chicks fledged.

Stephen Kress, the ornithologist who pioneered social-attraction techniques more than 40 years ago, says he can’t believe what came out of a few decoys and a boom box blaring puffin calls on Eastern Egg Rock Island.

“That’s really the most exciting part of this,” Kress says. “We developed the method for one application, but that’s really only a small piece compared to all the other successes.”

Correction: An earlier version of this article implied that social attraction experiments and nest monitoring studies of Marbled Murrelets by Oregon State scientists were related and occurred at the same time and place; in fact they were conducted separately at different locations in the Siuslaw National Forest.

Carrie Arnold is a freelance science writer whose work has appeared in the Washington Post, Scientific American, Audubon, and Slate.