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Caught

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Thirty years ago, one of the great ornithological mysteries was solved—as most mysteries are—with luck, lab work, and dogged deduction

Academy of Natural Sciences of Philadelphia/Corbis

Academy of Natural Sciences of Philadelphia/Corbis


By Maria Mudd Ruth '82

The downy chick lay lifeless in Laurence Binford's hand. Its body fit snugly into his outstretched palm, its slender beak at his fingertips, its delicate webbed feet extended back and lightly touching his wrist. Binford had never held such a bird, nor seen one, even through binoculars. He'd been thrilled when Bruce Elliott, a biologist for the California Department of Fish and Game and a longtime birding pal, phoned him about the bird, though he was saddened that he couldn't have seen it before it died—just one night after its rescue. Elliott and the rangers at Big Basin Redwoods State Park had no doubts that the bird was a marbled murrelet, but Laurence Binford was the man who would prove it scientifically.

In August 1974, Binford, then 39, was an ornithologist and a recognized authority on the birds of California and Mexico. He was also the assistant curator of birds and mammals at the California Academy of Sciences in San Francisco. He had seen marbled murrelets, adults and juveniles, at sea many times. He had even written about their great mystery—that no one had ever seen a marbled murrelet's nest—in his Birds of Western North America. Binford didn't have the time or the inclination to search for a nest, even though it turned out that his office was less than an hour's drive from the old-growth forest where the chick had been found. He spent his time with other birds, more than 100,000 of them, preserved as study skins in the academy's collection. Binford knew that someday a birder or ornithologist would come upon a marbled murrelet nest, but he never imagined it would be so high in a tree, so out of sight and reach.

Evidence was mounting to support the theory of tree nesting, but only a handful of ornithologists believed it possible, or probable. Alcids—a family of web-footed seabirds to which the bird belonged—were notoriously fast but awkward fliers, capable of swimming underwater in the style of penguins, but with poor records for smooth, precision landings. How could a marbled murrelet navigate its way in and out of the deep forest without hitting trees like a pinball? How could the bird survive dozens of flat-footed crash landings on the short runway of a tree branch? Binford's colleagues were skeptical.

Yes, Binford acknowledged, a tree was a bizarre place for a web-footed seabird, but he also knew that nature embraces the anomalous, unlikely, and strange with arms wider than the human imagination.

By placing the bird in Binford's hands, Elliott—and, by extension, the California Department of Fish and Game—had given him the responsibility of describing the chick and its nesting habits to the world. Binford would have to create a document, in the form of an article in a peer-reviewed scientific journal, proving that the chick was in fact a marbled murrelet and that the mossy patch on the limb was in fact its nest. Every feather, bone, organ, bit of moss, and chunk of branch would be evidence, requiring examination, comparison, and analysis.

The nesting site would no longer be unknown or mysterious. Rangers and biologists would return to the discovery site to measure the height and diameter of the nest tree; the diameter, length, and orientation of branches near the nest limb; and the distance from the tree to the nearest point on the Pacific. They would provide the names of the trees and bushes surrounding the nest tree, the percent of canopy closure, the names and location of nearby streams, climate and fog data, and the pattern of sunlight at the campsite. Once everything relating to the discovery of this chick became factual and familiar, Binford's report would be reviewed by several of his peers and then published—the same time-honored approach to documenting discoveries that Charles Darwin and generations of scientists after him had followed.

The job of documenting the evidence—the work that turns a find into a discovery—would require several months, but Binford happily accepted it.


FOR BINFORD, the process of discovery began on the roof of the California Academy of Sciences building overlooking Golden Gate Park. Set in the center of the roof is a small structure resembling a garden shed. This humble structure is the skinning lab, where freezers full of dead birds and mammals await "preparation." The stench of animal carcasses hovers amid a chaos of plastic buckets, cardboard boxes, metal trays, and tables covered in piles of papers and books. At a central table, preparators can be found hunched like surgeons over sea otter or red-tailed hawk or rufous hummingbirds. With a variety of tools not usually found in a garden shed, they disassemble, dissect, examine, clean, stuff, and reassemble the animals for study or display.

Had the marbled murrelet chick been of less potential significance, Binford might have handed it over to one of the staff preparators. But he wanted to skin the fragile bird himself, to learn its secrets firsthand. He entered the lab and picked up a metal tray on which he placed a dissecting kit, gram scale, calipers, borax, cotton, needles, and spool of thread. He returned to his basement office where he laid out the lab equipment, opened a notebook, removed the dead chick from its ice-packed cooler, and placed it on the scale. The bird weighed a mere 95.6 grams, or 3.3 ounces. This could be normal, but Binford was careful to note that the numbers did not take into consideration loss of weight from unusual exertions, starvation, and freezer desiccation. There was no way to calculate the cost in trauma to the chick of two days of being handled and ogled.

Before Binford reached for the scalpel, he found a pencil and made a rough sketch of the pattern of spots on the chick's head and neck. The pattern might hold the code for determining the chick's age when it could be compared with other downy chicks—if and when others were found. In 1974, no natural history museum in the world had a downy marbled murrelet chick. Most had dozens, even hundreds, of adult and juvenile marbled murrelets in their collections. A few had downy chicks of other murrelets. What Binford had was unique.

Photo by David Forthoffer/AP Photo

Photo by David Forthoffer/AP Photo

As Binford sketched the dappled chick, he noticed that the down was attached to the tips of nearly full-grown feathers. It was apparently undergoing its first molt into juvenal plumage. That the chick retained down while molting was not unusual; many birds retain wisps of downy plumage even after fledging. What was strange was that the chick retained so much of it. When Binford gently stretched open one of the chick's folded wings, he discovered developed primary flight feathers, primary and secondary wing coverts, underwing coverts, and alular quills. This was a bird ready to fledge, but a bird still mostly covered in its natal down.

The chick's small, pointed wings angled out perpendicularly from its body and then swept sharply back at their midpoint—the high-speed design typical of falcons, swifts, terns, many shorebirds, and most alcids. Binford measured the small wing of the chick and the length of its tail and bill. He measured the tarsus and the middle toe. He measured the bird's egg tooth—the tiny protuberance on its bill that had helped it peck its way out of its shell some weeks earlier.

The chick now had a set of numbers, but without another marbled murrelet chick to use for comparison, the numbers meant little. Binford took the same measurements from six male marbled murrelet skins in the academy's collection. His comparisons revealed that the chick was more than three-quarters of adult size. He had no way to estimate the bird's age. No growth pattern for the species had yet been established.

Binford set the young bird on its back. He separated the feathers along its midline and cut through the bird's thin skin from sternum to vent with his scalpel. Snipping bones in its breast, wings, and legs, he opened up the bird and carefully examined the organs. The chick was, by evidence of paired testes, a male. Finding these organs (or ovaries in a female) was the only way at the time to determine the gender of a marbled murrelet. There is no known difference in size, shape, or plumage between males and females—a trait that scientists refer to as sexual monomorphism.

When Binford examined the chick's digestive tract, he found some partially digested egg yolk. During the chick's 24 hours in captivity, the wildlife rehabilitator caring for it had provided this as the standard meal for orphaned birds. In retrospect, it was a poor choice for a seabird, but not until 1991 did researchers observe a marbled murrelet chick eating: It swallows whole, small fish in one gulp.

Binford's chick had also eaten a few whole down feathers. Downy chicks of many species will pluck their own feathers and peck at and snap up loose feathers around the nest.

Binford weighed and measured the chick's organs and then placed them in a jar of preserving alcohol. He measured the fat on the inside of the skin near the feather bases. There was a moderate amount of fat, which he scraped away, careful not to tear the skin or loosen the feathers from their bases. He wondered if the unusually late retention of the down—rather than a thick layer of fat—allowed the chick to stay warm and still be light enough to fly to the sea on young wings. Certainly a heavy, fatty chick would drop like a stone from a lofty nest without a chance to get airborne.

Next Binford detached the muscle tissue from the bones and wings and gently rubbed the skin with borax to remove all traces of fat, so that the preserved skin would not rot. He stuffed small rolls of cotton into the skull and body cavity until the chick assumed its original volume and shape. With a zigzagging stitch, Binford sewed the bird closed. He spread open the webbed toes of one foot and gently closed the toes of the other. He crossed the bird's legs, left over right, and tied them together with a string attached to a small paper tag. On the tag in indelible ink, Binford wrote the bird's serial number (CAS 68895); the collection location (California, Santa Cruz Co., Big Basin Redwoods State Park, Campground J-1); and the collector (Hoyt Foster, a local tree trimmer). On the back of the tag, in pencil, he wrote the name of the bird: marbled murrelet, Brachyramphus marmoratus.


BINFORD LOOKED at the bird. The downy feathers were still soft and fluffy, the juvenal feathers glossy and intact, and the head tucked and cocked naturally. Were it not for the chick's white cotton eyes, the bird looked poised to fly right out of his hand. It was lifelike to be sure, but Binford's work was just beginning. He had to work quickly to describe the colors of the chick's feathers before they began to fade. He could have taken the easy way out and described the chick as "buff colored with some black spots on the head," but as birders, artists, and housepainters know, one man's buff is another man's beige, and black isn't necessarily black.

To describe the color of the chick, Binford needed a color standard—a set of colors created systematically. Color standards usually take the form of a chart, wheel, or book of color plates. Not all color standards are created equal. Some are intended for artists, others for housepainters, mineralogists, botanists, printers, mapmakers, textile dyers, crayon manufacturers, anyone needing to match or reproduce a certain color exactly. Binford found most color standards were too bright, too electric, and too acrylic for the subtle variations of hues and tints of feathers. For him and for most every ornithologist, there is only one color standard for birds. It is Robert Ridgway's Color Standards and Color Nomenclature.

Since its publication in 1912, Ridgway's book has found its way onto a shelf in every natural history museum library in North America. Robert Ridgway was an ornithologist, author, and painter in the era after Audubon and before Kodacolor. From 1874 to his death in 1929, he was the curator of birds at the Smithsonian Institution in Washington, D.C. He knew firsthand the problems of reproducing and naming the colors of the natural world. He worked on the problem for 20 years, including three years on the reproduction of the color plates for his volume. He based his system on 36 pure, solid colors, to which he added carefully prescribed amounts of black and white pigments. The resulting 1,115 colors are presented on one-inch-square plates cut and glued to thick pages separated by sheets of vellum. Each color, including 22 shades of black, has a name. Using Ridgway's book, an ornithologist in Baton Rouge can describe a bird as having an Olivaceous Black nape and a Buckthorn Brown supercilium, and every ornithologist east and west of the Mississippi will know exactly what he means. The book is a masterpiece, indispensable.

It is also unstable. "CAUTION!!!" Ridgway warned readers on the page preceding the color plates, "DO NOT EXPOSE THESE PLATES TO LIGHT FOR LONGER THAN NECESSARY." Ridgway had gotten his colors onto paper in 1912, but he couldn't guarantee they would remain fixed there. He took great pains to use the most durable pigments available at the time, but certain colors could only be reproduced with pigments that were light sensitive. "Green and violet aniline dyes are all very evanescent," he wrote, "rapidly fading and eventually disappearing." To avoid such a fate and the corruption of the color standard, most libraries wrap the book in black cloth and store it in a locked cabinet. The book is never used in direct sunlight and is only viewed for very short periods of time. How well this book suited the secretive and crepuscular marbled murrelet.

Photo by David Muench/Corbis

Photo by David Muench/Corbis

Binford brought Ridgway's book from the academy's library into the natural, indirect light of his office. Glancing between bird and book, plumage and plate, he found exactly what he was looking for. The feathers on the chick's head and neck were Light Ochraceous-Buff marked with 27 spots of Sooty Black. Its throat and upper parts were Pale Ochraceous-Buff. Its abdomen was feathered in Pale Smoke Gray and Light Buff. Its sides and flanks were shaded in feathers colored Pale Smoke Gray at the base, Deep Mouse Gray at the middle, and Light Ochraceous-Buff at the tip.

Plate by plate, this chick acquired the weight and beauty of poetry, the rich language of color. The open vowel sounds were luscious and soothing: Ochre evoking iron ore, Buff the color of certain bare skin, Smoke the ephemeral world. Pale and Light are suitably subduing modifiers for a bird of the dawn and dusk.

As fanciful as the names sound, they are not Ridgway's invention. With the eye of a scientist and artist, he selected them carefully from two existing sources. One was a color standard commissioned by the American Mycological Society for identifying mushrooms. The second was a collection of colored Japanese silks, taffetas, velvets, and other dress goods sent to Ridgway from the now defunct Woodward & Lothrop department store in Washington, D.C.


SATISFIED THAT he had recorded every visible color and had left nothing unmeasured or undescribed, Binford carried the chick in the lid of a cardboard box toward the metal collection cabinets. He placed it in a corner of a drawer holding two dozen marbled murrelets—all adults, all laid out in rows on their backs in the mothball-scented air. Nothing could have been further from the mossy branch of a Douglas fir.

Now, Binford had to make sense of the nest. The day after the chick was found, Hoyt Foster had climbed back up the Douglas fir to remove the limb and lower it in sections to the ground, taking special care to keep the nest intact. What Binford ended up with—what was now sitting on his desk—was a chunk of the limb 12 inches long and 15 inches in diameter, covered with moss and bird droppings that were redolent of fish and, to Binford, not unpleasantly reminiscent of a marine bird colony.

The nest was little more than an oblong depression or "bowl" in the bark of the limb. Binford judged this bowl to be natural since he detected no bill or claw marks that would indicate a bird had shaped the nest by removing flakes of bark. The bowl was large enough to accommodate one of the marbled murrelet's chicken-sized eggs, or one chick—no more. The size of the nest supported evidence that this species laid single-egg clutches.

Hoyt Foster had reported that moss grew thickly along the entire length of the branch—green on most of its length and then brownish as it surrounded the nest bowl. But no moss grew inside the nest bowl. A botanist at the academy identified the moss as Isothecium cristatum, a species commonly found in California's moist coastal forests. The botanist could think of nothing that would prevent the natural growth of moss in the bowl or that would turn the moss around the bowl brown. Nothing, that is, but marbled murrelets. Binford suspected that the moss had been worn off inadvertently by chicks and adults over a period of time, and not in just one nesting season. The missing moss was the first evidence of philopatry—the practice of returning to the birthplace to breed—among marbled murrelets.

Binford examined the moss, which apparently served as an underlying meshwork for the thick layer of droppings that ringed the bowl. In terms perhaps more poetic than the subject deserves, he described the droppings as "smooth, rounded, slightly glossy hillocks that varied in color from buffy-white to Cream-Buff." The latter color (from Ridgway) was strikingly close to the Pale Ochraceous-Buff of the chick. Through his painstaking color matching, Binford had broken a code, tapped into a language in which colors reveal secrets.

The buff colors told Binford of a chick adapted for survival on the nest. As long as the chick retained its buff-colored downy plumage, it remained camouflaged against buff-colored droppings. The down hid the chick's striking black-and-white juvenal feathers as they emerged beneath it. In a world of Cream-Buff and Light Ochraceous-Buff, the chick remained nearly invisible to predators—whatever they were. This would explain the late retention of down that Binford noted.

Binford reached for the tweezers. From the ring of droppings and surrounding moss, he fastidiously picked out approximately 165 eggshell fragments ranging from smaller than the head of a pin to the size of a raisin. With the naked eye, hand lens, and microscope, he noted the colors of the fragments and the spots that marked some of them. The background color of the egg, according to the Ridgway standard, was Pale Glass Green. The spots were Lavender-Gray, Deep Madder Blue, Sepia, Bone Brown, and Saccardo's Umber. The names alluded to and commingled the worlds of wine bottles, fragrant herbs, pigment-rich plant roots, cuttlefish ink, fossilized skeletons, and gave a nod to Pier Andrea Saccardo (1845–1921), a man who spent 35 years of his life compiling a 160,000-page list of all the common and scientific names that had ever been used for fungi.

These richly evocative color names described an eggshell, but, Binford wondered, were they the colors of a marbled murrelet eggshell? Binford turned to a brief scientific article, written in 1941 by ornithologists G.M. Sutton and J.B. Semple, that described an egg taken from the oviduct of a female marbled murrelet collected in British Columbia. These authors also cited Ridgway's colors, ones that closely matched those that Binford had chosen and were unlike the colors of the eggs of any other alcid species.


ON THE nest, a marbled murrelet is almost chameleonlike in its development of coloration from egg to chick to juvenile to adult. The egg blends in with the dappled moss freshly green after winter rains. The downy chick matches colors in the tree bark, the fallen brown needles of the tree, and the ring of droppings surrounding its nest. Adults in their cinnamon-brown breeding plumage blend in with the bark of the nesting trees and the browned moss and needles around the nest. All the clues, all the pieces of the puzzle, were fitting together. Finally. Buoyed by the strength of the evidence at hand, Binford turned to the scientific literature. Here, in the journals of natural history clubs and ornithological societies, he found plenty of evidence for tree nesting. All of it, however, was indirect or circumstantial.

Beginning with George Cantwell's stories from the Haida Indians of British Columbia in 1897, Binford followed the evidence presented in articles by Darcus, Dawson, Gabrielson, Guiguet, Harris, and others. What he found were stories of nest searches (many—all failed), egg discoveries (one indubitable, several questionable), chicks found on the forest floor (a handful, possibly fallen from trees), sightings of marbled murrelets flying inland (hundreds, destination unknown), a variety of nesting theories (all unproven), and a wealth of information about the bird's biology and breeding behavior (now, in hindsight, pointing to one inevitable conclusion). The most recent article he read had been published in January 1974 in the journal Auk: "Evidence for tree nesting in the marbled murrelet is mounting," wrote a young Canadian ornithologist, Spencer Sealy.

In January 1975, after months of laboratory and library work, Binford drove down the coast highway to visit the nesting site at Big Basin Redwoods State Park. He met with Bruce Elliott and the rangers who, with Hoyt Foster, had been involved in caring for the chick and describing its nest the previous summer. He walked up the path toward the campground to the Douglas fir, and gazed up the trunk at the metal plate covering the cut where Foster had removed the nesting limb. The height was astonishing. There would have been no way for anyone on the ground to see a nest of any sort on a limb that high. Even if Binford could have seen it, he wasn't sure he would have believed it. It was a strange place for a seabird's nest.

Binford completed his report in March 1975 and submitted it to the Wilson Bulletin, the quarterly journal of the Wilson Ornithological Society. He had considered other prestigious journals, Auk and Condor, but only the Wilson Bulletin could publish the color photographs he had—one of the live chick in all its buffy glory taken by Elliott and one of the humble nest on the cut limb. The article was reviewed by two ornithologists and accepted in May. In September 1975, "Discovery of a Nest and the Downy Young of the Marbled Murrelet" appeared in print.

The report ran 18 pages, with a black-and-white photograph of the entire 225-foot Douglas fir and a sketched profile of the spotty-headed chick accompanying the color photographs. The chick had been written into the record, introduced to the world as a marbled murrelet, Brachyramphus marmoratus, a bird found and then discovered. Its nesting site was no longer a mystery, a vexation, a Holy Grail, a "stigma on oologists" as one naturalist called it. It was a bowl in a mossy branch, a natural depression, a Cream-Buff ring of droppings, a very small niche on a large planet.


TWENTY-FIVE years after Binford's report was published, I stood in the basement of the California Academy of Sciences in San Francisco holding the marbled murrelet chick in my own hand. It was about the size of a starling—larger than I imagined it would be. It looked less like a downy chick than it did a dark-feathered juvenile hiding (badly) in a too-small fur coat—like a wolf in sheep's clothing.

I had brought Binford's article with me. I opened it to the photograph taken of this tiny bird alive on the day of its capture. There on the table before me were two chicks. One was a 25-year-old preserved specimen under fluorescent lights; the other was sitting in dappled sunlight captured in a color print made from a Kodachrome slide. Which chick did Binford describe? Which one did Hoyt Foster reach for in the Douglas fir? Which chick was closer to the truth? The truest colors of the chick now existed only on the small color plates of Ridgway's masterpiece. I picked the chick up in my hands.

I held the bird for a long time. I stood there with my arm extended, my hand cupped like a nest. I imagined the chick warm and alive in the Douglas fir. Had this chick happened to elude the tree trimmer and then its predators during its first summer, the mystery of the marbled murrelet would have ended perhaps with another bird in another forest somewhere on the Pacific Coast. This chick would have remained on the tree limb in the Santa Cruz Mountains, waiting for food, waiting for flight, growing. At dawn and dusk, its parents would have appeared with fish. Very gradually, the down would have disappeared from the chick's forehead and mandibles. A week later, from its belly. And in another week from the sides of its body. The chick would have felt a sudden burst of energy and the need to preen, scratch, and flap its wings. In its last eight to 48 hours on the nest, the chick would have lost its last bit of camouflage. Some of the down covering its back would have been scattered over the moss or trapped in the droppings. Most of it would have floated to the forest floor.

I imagined the chick exposed and vulnerable on its nest in black-and-white plumage, its instincts shouting, "Fly!" Where did the bird hold these instincts? In its brain or muscles or in the feathers or spaces between? Was I holding them in my hand? Somewhere still was the urge to step to the edge of its nest. Somewhere was the longing for the fish, the salt water. What no scientists knew in 1975—but what scientists would learn many years hence—was what happened next: Just after dusk, the chick would have spread its wings, flown off the nest, and headed west to the sea in one direct, original, and beautiful flight path.

 

Maria Mudd Ruth '82, a former researcher and writer for the National Geographic Society and editor for Traveler magazine, has published more than a dozen books on natural history topics. Her essay is drawn from Rare Bird: Pursuing the Mystery of the Marbled Murrelet, © 2005 by Maria Mudd Ruth. Permission granted by Rodale, Inc.

 


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