The Neglected Abundance of Your Backyard

It started with a thump, the grim sound of a bird hitting the window of my little office shack. When I ran outside to check, I found the first hermit thrush that I had ever seen in our yard, lying dead in the grass. As I lay those few feathered ounces to rest beneath a rose bush, my sorrow was tinged with something like embarrassment. Here I was, studying nature and writing books about it, and I’d had no idea that this celebrated bird was wintering in the shrubs just a few feet from my desk.

In biology, hermit thrushes are renowned for singing two tones at once, phrasing their notes in precise harmonic intervals eerily similar to the minor chords and scales used in human music. The resulting song is so haunting and beautiful that it has become a powerful metaphor in literature, invoked by hundreds of authors and poets since before ornithologists even knew which bird was responsible.

T. S. Elliot put a hermit thrush in “The Wasteland,” for example, and Walt Whitman called upon its “wondrous chant” to convey the nation’s grief in his famous elegy for Abraham Lincoln, “When Lilacs Last in the Dooryard Bloom’d.” As a biologist and a writer, failing to notice a species so famous in both of my chosen trades begged an obvious question: What else was I overlooking in my own backyard?

Finding answers would occupy years. I climbed trees, I dug holes, I crawled on my hands and knees, and I sat inside a pile of sticks, listening and watching. I saw an incredible array of species doing things that I had never imagined, from yellowjackets sipping honeydew in the treetops to woodpeckers dropping branches on a saw-whet owl. And when my research expanded to other yards and other neighborhoods, I learned that biological mysteries occur everywhere, even in the most urbanized landscapes on the face of the planet.

Few examples make that point better than a story that begins with a wager at a lunch party. “I had been bragging, perhaps unwisely, that I could find a new species anywhere,” Brian Brown told me over a Zoom call. His dark hair and boyish face belied more than 30 years of employment at the Natural History Museum in Los Angeles, where he currently serves as curator of insects. He made that fateful “new species” boast at a donor luncheon, and one of the museum’s trustees immediately took up the challenge. If Brown could find a new species of insect in her backyard, she told him, she would host a grand dinner party fundraiser in celebration. To add a bit of pressure, she went ahead and scheduled the party.

“I didn’t manage to get the trap set up until three weeks before the dinner,” Brown recalled, but any angst he felt about the situation disappeared as soon as he brought the first batch of specimens back to his lab. With a practiced eye, he began sorting out small, dark flies in the family Phoridae, his specialty. “The very first one I looked at didn’t key out to anything,” he said, referring to the technical manuals, or “keys,” used in taxonomy to tell one species from another.

To someone of Brown’s experience and expertise, that could only mean one thing. “It was unknown!” he said, still visibly excited years after the fact. The second fly he examined had “a weird leg,” and turned out to be the first North American record of a species known only from Europe. Then he found one from a genus never before recorded west of the Rocky Mountains.  “I didn’t even have to finish looking through the sample,” Brown went on. “I already had enough for the party.” More than that, he had confirmation that backyards in cities were worthy of exploration. And that gave him the beginnings of an ambitious new research program.

“The BioSCAN project is unique,” Brown explained, ticking off the features of an effort now in its 11th season. Where most biodiversity surveys explore rural places and wildlands, BioSCAN is focused on greater Los Angeles. And where most surveys inventory a wide range of life forms, Brown’s group decided to “go narrow and deep,” studying specific insects like phorid flies and bees. They’ve sampled from the urban core to the edge of the city, and from the coast inland to the desert, and they have consistently avoided designated natural areas, targeting instead the sorts of places usually overlooked by biologists — backyards, gardens and small neighborhood parks.

The results have been no less remarkable than those first few flies from the trap in his trustee’s yard. “There’s no end to it!” Brown exclaimed. “Every time we sample in a new area, we get new species.” For phorid flies alone, the team has discovered 50 new species, and expanded the known ranges of scores of others, and they still have thousands of specimens left to examine.

To Brown, the success of BioSCAN’s backyard strategy is gratifying, but not surprising. He finds similar untapped diversity wherever he looks for flies. Phorids are his forte, but the entire fly order remains poorly known. Over 160,000 species have been described, with perhaps 10 times that number waiting to be discovered. Or maybe more — nobody knows for sure. As Brown put it, “The magnitude of the richness, and of our ignorance, is beyond what we’re used to thinking about.”

When it comes to backyard biology, our ignorance extends far beyond putting names to all the flies and other creatures. We have even less idea about what they’re doing, but some researchers have begun asking the right questions. Behavioral ecologist Barbara Klump, for example, put a very specific query to the residents of Sydney, Australia: Had they ever seen a parrot opening the lid on their garbage can?

“We were also interested to know if they hadn’t seen it,” Klump clarified when I reached her on a video call. “It was crucial that we also could say where the behavior doesn’t happen.” By including that key detail in her protocol, and by racking up reports from over 1,300 participants in 478 different suburbs, Klump was able to pinpoint three neighborhoods where the bin-opening technique had been mastered.

It helped that the behavior was so distinctive — anyone would notice a parrot strewing garbage around their yard. It also helped that the bird was so distinctive — among Australia’s 57 parrot species, only one is large and snowy-white, with a comical plume of yellow feathers flopping around on its head.

“Sulphur-crested cockatoos are really ideal for this kind of study,” Klump told me. Intelligent and highly social, the birds live in what she called a “fission-fusion” system, dispersing in small flocks to forage during the day (the fission), and then gathering together again at large communal roosts to spend the night (the fusion). “The foraging parties change constantly, giving them lots of opportunities to learn behaviors,” she explained, and that learning process lay at the heart of Klump’s research interests.

After making a name for herself studying tool use in Hawaiian and New Caledonian crows, Klump embarked on the cockatoo study as part of a postdoctoral fellowship based at the Max Planck Institute of Animal Behavior in Germany. The project took shape quickly as soon as she and her colleagues documented the bin-opening behavior and showed that it was brand new, limited to just a few birds in a handful of locations.

“Oh my god!” she said, remembering her first glimpse of a cockatoo in action. “All of these questions started coming in. How do they figure it out? Do they all do it in the same way? Is this a socially transmitted behavior?” Finding answers would require a lot of data, far more than she and a few student-helpers could ever accumulate on their own. “We couldn’t have done it without the citizen scientists,” she said, and explained how she continued her online surveys for years, gathering observations from thousands of residents across greater Sydney. Some of them still keep in touch with her, sending pictures, notes and videos of bin-opening and other cockatoo antics playing out in their neighborhoods.

Because Klump’s team had thought to document both the presence and absence of bin-opening cockatoos, and because they had spotted the behavior so soon after it began, they found themselves in a position to map its spread. From those three original neighborhoods, the ability to open garbage bins swept through cockatoo populations in an additional 41 suburbs in only two years. And as it diffused, the behavior began to change.

“It’s a difficult task for the birds,” Klump explained. “They try and try and often fail.” That profusion of repeated attempts gave the cockatoos ample opportunity to experiment and to develop variations on the original technique. Some grabbed the lid with their bills, others used a foot, or a foot and their bill together. Some walked to the right along the rim; others went to the left. Some birds side-stepped, while others walked straight. Those nuances could be mapped, too, and it quickly became apparent that the birds were doing more than just learning from one another; they were developing distinct neighborhood styles. And when a socially-learned habit begins to vary geographically, taking on unique traits in different populations, behavioral ecologists have a word for it: culture.

With Klump’s findings, sulphur-crested cockatoos joined the likes of chimpanzees and certain whales and dolphins among the few wild species with documented forms of culture. But the backyard discoveries in Sydney didn’t stop there. Continued observations revealed that people had begun responding to the birds, protecting their garbage bins with rubber snakes or weighing down the lids with bricks. Those behaviors also varied by geography, as people copied what their neighbors were doing, and as the cockatoos learned to overcome their various defenses. Klump calls this interaction an “innovation arms race,” and it’s a good reminder that what we see in our backyards is a two-way street — it affects us, too.

When that poor hermit thrush hit my office window, I immediately went out and bought a roll of translucent bird tape, put it up, and haven’t had a bird strike since. Simple fixes sometimes produce significant results, and with a little effort, backyard biology can be about more than identifying and observing other species. We can also do things to help them, boosting the biodiversity of virtually any patch of ground. In our yard, that effort included nurturing a patch of shrubs that were struggling to get established beside the driveway.

That should take care of it, I thought, stomping with my heel to pack dirt and gravel around the base of the new signpost. For several years, my efforts to nurture a patch of thimbleberry bushes at the head of our driveway had been repeatedly thwarted. They’d come up on their own, a native species related to the common garden raspberry that would bear similarly delicious fruits if they ever got a chance to mature. But while I’d been careful to trim back the brush and grass around them, their position near the road made them vulnerable to our local county maintenance crew. Twice in a row, just as the canes got tall enough to flower, a passing mower had whacked the whole thicket back to ragged stumps. This season, I was determined to prevent that from happening again. With the thimbleberries once more grown robust, leafy and ready to bloom, I had put up a notice to keep all would-be shrub cutters at bay.

Stepping back to admire my handiwork, I stopped short and found myself doing the sort of cartoonish double-take usually reserved for slapstick comedies. Was I losing my mind? The words I’d painted on the sign made no sense — worse than that, they encouraged the very behavior I was trying to stop! It seemed impossible, but there was no denying the instructions now printed beside my precious thimbleberries in large block letters: “MOW ON.”

If you turn those words upside down and read the phrase again, you will immediately see my mistake. I’m happy to report that once the sign was properly oriented, it served its purpose admirably, and our thimbleberry patch has been thriving ever since. In springtime, we always enjoy its flush of broad green leaves and pale flowers, followed in early summer by a tasty harvest of small crimson fruits. Those rewards were an ample return on investment, but to be honest, I considered them something of a side issue. It wasn’t until I spotted a woody burl gnarling one of the canes that my true goal was realized, and I knew that in one fell swoop, I had increased the biodiversity of our yard by as many as 14 species.

In botany, the word gall refers to any lump, swelling, or other abnormal plant growth spurred by the activities of another organism. Usually, that means an insect. Gall comes from the Latin term galla, or “oak-apple,” a direct reference to the large, spherical knobs that often form on the leaves and twigs of oak trees. These and other galls were gathered throughout the ancient world for use in dying fabric, making ink, and tanning leather.

Many also had medicinal value, mentioned by the likes of Hippocrates and Pliny the Elder as treatments for everything from hangnails to toothaches, bleeding gums, ear infections and dysentery. Galls were readily available for purchase in the shops of Herculaneum, just down the road from Pompeii, where a vessel containing over 2,800 oak galls was entombed and preserved by the eruption of Mount Vesuvius.

During the Middle Ages, fortune tellers added augury to the checklist of handy uses for galls. Opening one and finding a maggot inside signaled a coming famine, for instance. If the gall contained a spider, pestilence was in the offing. To British author Beatrix Potter, galls from rose briars were known as “Robin’s pincushions,” a popular plaything for the title character of her story, “The Tale of Squirrel Nutkin.”  All of these examples demonstrate that people had learned to recognize and find uses for plant galls long before they understood how or why they formed. That knowledge came later, much of it from a single person, a scientist who was perhaps better known for his work in a rather different field of study.

To most people, the name Alfred Kinsey brings to mind a pair of groundbreaking and controversial books on human sexuality. With the 1948 publication of “Sexual Behavior in the Human Male,” followed by a companion volume on female behavior five years later, Kinsey firmly established himself as one of the most famous (and infamous) scientists of the 20th century.

To entomologists, on the other hand, “The Kinsey Reports” were an unfortunate diversion from an otherwise illustrious career. Before turning to sex research, Kinsey devoted decades of his life to the study of gall wasps, the tiny insects responsible for deforming my thimbleberry canes. It’s hard to overstate the scale of his contribution. While the 8,000 interviews that Kinsey personally conducted about sexuality may sound impressive, that’s nothing compared to the attention he showered upon wasps.

From the time he encountered his first gall, on a field trip while studying at Harvard University in 1917, to the end of his last collecting expedition in 1939, Kinsey and his student helpers gathered and processed over 7.5 million specimens. Kinsey’s wasps now reside at the American Museum of Natural History in New York, where they make up a staggering 40% of the entire insect collection. The numbers alone are impressive, but Kinsey and his team also studied biology and behavior, rearing hundreds of different species in captivity and opening a window into the fascinating struggle for reproductive dominance taking place inside each and every gall.

Some wasps produce an enzyme that tricks the plants into making tasty gall tissue for their larvae to feed on. Other wasps are freeloaders or parasites of the gall makers. There are even parasites of the parasites. Some wasps mate on the surface of the galls, some mate on nearby flowers, and some don’t mate at all, cloning themselves in alternate generations. After decades of studying such bizarre reproductive strategies, it’s no wonder that Kinsey became a sex researcher. In fact, he may well have found human mating habits rather dull in comparison!

From parrots and trash cans to wasps and Alfred Kinsey, the stories behind backyard species, even inconspicuous ones, are often surprising. But investigations and habitat restoration aren’t the only reasons to pay attention. There is a more personal benefit to spending time with nature close to home: How other species make us feel.

In 1984, a two-page report appeared in the journal Science describing a simple study from a small suburban hospital in Pennsylvania. The authors analyzed 10 years of data on patients recovering from the same gallbladder surgery in the same ward, where only one thing was different about their care: some had a view out their window of a grove of trees; others looked out at a brick wall.

In case after case, the results were the same: Patients with a view of trees recovered more quickly, required fewer painkillers, made fewer calls to the nurse’s station and experienced fewer complications from their surgery. To be clear, the trees in question were not towering old-growth behemoths, breathtaking in their majesty — it wasn’t necessary to be awed to be affected. Simply the presence of typical suburban maple trees, viewed through glass, was enough to enhance the process of healing.

In the decades since its publication, the hospital bed study has become the research equivalent of a runaway bestseller, cited by more than 8,000 other papers that bear out and expand upon its findings. Confirmed positive effects of nature on human health now range from stress reduction to lowered blood pressure, reduced cancer mortality, lower incidence of diabetes, and, for pregnant mothers, higher infant birth weights. The evidence is so overpowering that it is now possible to receive a medical prescription for nature exposure from doctors in 35 states, four Canadian provinces, and dozens of countries around the world, including Japan, where the remedy is charmingly referred to as “forest bathing.”

I gave myself a backyard prescription on a sunny summer day when I was suffering from a rotten head cold and couldn’t get much writing done. Outside, I retreated to a patch of compacted sand and gravel on our property where I had been planting wildflowers, trying to attract native bees.

The effects of fledgling bee gardens on human health have yet to be studied directly, but I still viewed my time outside as a form of self-medication. Truth be told, my head cold wasn’t the only thing making the day harder to embrace than most. Other life stresses were involved, and, as the saying goes among biologists, “nature is cheaper than therapy.”

I found a patch of gravelly soil warm from the sun and lowered myself down to sit amongst a scattering of wildflowers — the pink topknots of sea blush, the vibrant stars of blue-eyed grass, and the rosy, four-petaled faces of farewell to spring. There was a faint breeze making the blossoms nod, as if tugged by invisible strings, and I noticed the leaves of a gumweed I’d planted and forgotten all about — small, but still surviving in the thin, dry soil. Then a bee appeared, a jet-black miner with a wash of tawny fuzz like a velvet stole across its thorax. I watched as it hovered and drifted back and forth, inches above the cobbles and vegetation. It was a species that I’d never seen before on our property, a ground-nester more common in the remnants of native prairie that dot our island’s shoreline, several miles distant. Would it nest here?

I held my breath when the bee landed, but then lost sight of it as it crawled off amongst the tufts of grass and wildflowers. My mind drifted, and a few minutes later, I decided to heave myself up and head back to the office for another try at indoor work. Just then, a furtive motion caught my eye near the base of a bunchgrass. Turning, I saw it again and felt a rise in spirits beyond the measures of science. It was sand, a flicker of grains flung skyward by tiny legs. The bee had begun to dig.