The sun is rising as Sonia Hernandez and three research assistants unload a canoe and inflatable paddle board. A University of Georgia wildlife disease researcher, Hernandez urges everyone to hustle; she’d like to embark for their destination—a cluster of tree-filled islands around a bend in the stagnant water—before the neighbors wake up. It’s taken some convincing to get permission to be here. The fewer questions, the better.
On cue, a security guard pulls over to investigate but soon departs on a note of friendly caution: “Be safe, there’s gators out there, ladies.”
Curious bystanders armed with gator wisecracks will continue asking questions in the coming weeks, but they won’t faze graduate student Julia Silva Seixas. She’s here for the White Ibis, one of Florida’s most abundant and iconic wading birds. The islands host a breeding colony, and Seixas will spend the spring deploying camera traps and monitoring nests.
White Ibis don’t undertake annual migrations. They are more nomadic, roaming widely and haphazardly within their range, which encompasses all of Florida and coastal areas of the southeastern United States, Mexico, Central and nothern South America, and the Caribbean. University of Florida ecologist Peter Frederick calls them “boom or bust” birds. With long beaks and legs designed to forage in shallow water for small invertebrates, the species is perfectly evolved to take advantage of annual fluctuations in marshy ecosystems. When a wet year follows a drought, ibis feast on crayfish ahead of slower-to-react competition and their numbers swell—such as when scientists documented a record 95,000 nests in the Everglades in 2018. But ibis readily go elsewhere in times of food scarcity. “When they move on, they really move on,” Frederick says. “They are a sensitive marker for what’s going on in the Everglades system.”
Scientists like Frederick closely track the health of this vast River of Grass. A century of dike-building, agricultural development, and population growth has drained and destroyed roughly half of the original Everglades and degraded the quality of what remains. An unprecedented restoration effort is now attempting to revive the ecosystem, which supplies drinking water and hurricane protection to the region and habitat to dozens of threatened and endangered plants and animals, including Florida panthers, Snail Kites, Cape Sable Seaside Sparrows, and Wood Storks.
White Ibis, however, are not in any particular jeopardy. In fact, these opportunistic birds are realizing new possibilities in encroaching human habitats—a trend that Hernandez has been documenting in suburban Palm Beach County for more than a decade. Rather than probe natural wetlands for food, here ibis poke at soil for a predictable meal of insects or worms from irrigated lawns of subdivisions, golf courses, and local parks. Typically wary of humans, birds step right up to park-goers who offer them bread, which fills them up but lacks nutrients and vitamins they need. Some will even eat trash, says Hernandez—or (debatably worse) Flamin’ Hot Cheetos.
As the breeding season begins, ibis largely keep to the Everglades or other nearby wetlands to nest. But this is no such natural area. Hernandez’s canoe attracts attention because the rookery sits in the middle of the PGA National Resort & Spa, a sprawling golf, hotel, and gated condo complex in Palm Beach Gardens. Not many people paddle these waters. To better blend in going forward, Hernandez advises the students to dress like joggers and wear binoculars beneath their shirts.
Though street-smart, carb-loading ibis are only a small portion of the state’s population, Hernandez suspects the species’ taste for suburban life is escalating. In study after study, she’s taking a rare, detailed look at this progression as it happens, hoping to understand what it means for the bird’s future.
“White Ibis are kind of like sheep, in a way. They’re afraid to do new things, but once one individual does it, they follow,” she says. “We’re on a crusade to figure out whether urbanization is good for them or not.” This season’s campaign aims to shed light on the health of the golf course’s nestlings. With helmets packed to protect from errant balls, the team pushes off into the water and steers in the direction of Hole Six on the Champion Course.
Pigeons are love-or-hate birds. American Crows, Canada Geese, and gulls are, too. Some people appreciate these animals’ wiles and everyday beauty or seek to feed and attract them. Others loathe their noise and droppings and chase them away, sometimes with help from pest-control firms.
Large and often regal-looking, wading birds aren’t usually so polarizing. But that’s not always true, especially when they cozy up to people. In South Africa, the drabbish brown Hadeda Ibis, sometimes dubbed the “flying vuvuzela” for its unrelenting calls, has been described as an “agent of chaos” in the news, even as some residents welcome its help aerating garden soil. In Spain, where Hernandez grew up, nesting populations of the fabled and once-declining White Stork have soared since the 1980s, thanks partly to their feasts at landfills. Locals would once knock the storks’ colossal nests from building tops, Hernandez recalls. Now the region has not only embraced the bird but also recognized its tourism value.
The most divided passions, perhaps, are bestowed upon the Australian Ibis, a more-than-two-foot-tall species native to that country’s rich inland marshes and a distant cousin of the Florida bird. Five decades ago, spotting one near coastal cities such as Sydney or Brisbane was rare. “If you saw an ibis at the local wetland, you’d race home and call up all your bird nerd friends,” says Taronga Conservation Society Australia research scientist John Martin. Today they’ve cracked the Top 10 most common birds spotted in BirdLife Australia’s Backyard Bird Count—and become a clear pest.
Dubbed “bin chickens,” “sandwich snatchers,” and “tip turkeys” for their bold, dumpster-diving ways, the birds nest by the hundreds in loud, smelly urban colonies. In 1995 the multimillion-dollar loss of a Qantas Airbus engine from an ibis strike sparked the creation of the Ibis Management Coordination Group. Today even small cities run efforts to control populations, and advocates and scientists have had to wage a campaign to remind the public the birds are still protected. (Haters, instead, had a chance to vent during a social media event: International Glare at Ibises Day.)
On the flip side, they’ve attained a fan base as they’ve multiplied. The birds are subjects of tributes that include artwork, tattoos, an animated series, and a Planet Earth mockumentary. In 2017 they took a surprise second place in a vote for Australia’s favorite bird.
Scientists struggle to account precisely for this urban ibis boom. In the 1970s several zoos released small groups of captive Australian Ibis to create “wild” exhibits—perhaps seeding unusually fearless populations. But these initial releases can’t explain the tens of thousands that breed in cities now, Martin says. One possibility is that urban birds dispersed and “spread the word” about good city life, attracting new arrivals that found refuge when conditions were poor in natural breeding areas.
For now, researchers aren’t sure how closely the marshland and metro populations are connected, since they’re hundreds of miles apart. What is clear: In roughly the past 40 years, ibis and other birds that breed in Australia’s interior wetlands have declined due to drought, habitat degradation, and other factors as urban ibis thrived. And though human food and trash aren’t exactly healthy, studies show the birds still consume natural prey (they eat from the salad bar as well as junk, as Martin puts it).
“In the city, they have abundant food, abundant freshwater, and abundant habitat. So we see birds breeding for longer periods than they would in the natural environment, and we see they don’t have to fly as far,” Martin says. In other words, Australian Ibis may not always score high in a popularity contest, but on the whole, they seem to be winning.
In Florida, the White Ibis are running late. They clock in most mornings to graze the lawn and seek handouts from visitors in Dreher Park, but Hernandez surmises they may be crashing feeding time at a nearby zoo’s flamingo enclosure. “The zoo hates them,” she says. “They lose so much food.”
Then some ibis show, and her team of current and former graduate students gets out homemade flip nets and leg lassos. Hernandez and her student Henry Adams devised the gadgets to capture adult ibis, so that the researchers can band them, measure body size and condition, and collect blood, a feather, and feces. (Ornithologists typically might use cannon nets, but the loud noise they produce isn’t ideal in the suburbs.)
Hernandez casually lures an ibis by offering bits of white bread with exaggerated motions, flicking her wrist as if slinging dollar bills toward the sky. The birds readily approach. When she first began this work, her team underestimated the species’ intelligence. They wore University of Georgia shirts to look official, but the ibis started to recognize and avoid them. Once banded, the birds were also difficult to recapture. This morning the ibis are evading the team’s efforts, lifting off in graceful bursts as soon as a net is flipped or a lasso is yanked. As the birds grow skeptical of the group, Hernandez encourages more subterfuge: “Don’t just stand there like statues,” she tells them, “act like you’re at a picnic.”
She’s a pro in these situations. Hernandez began her project in 2009, after taking notice of ibis running up to people to accept food handouts while visiting her parents at their condo nearby. “I thought, ‘This is just so bizarre that a bird that is so built for a very specific way of foraging would adapt in this way,’ ” she says. “And why them, and not other wading birds?” Her first research recruit was her husband, also a wildlife disease ecologist.
While they collected ibis feces off the ground to sample for pathogens (romantic!), she envisioned and then secured funding for a bigger project. She wanted to understand if the same birds were returning to eat a lot of “cheap, easy calories” day after day, season after season, and if so, whether that had changed their behaviors, patterns of movement and breeding, and overall health. Since then, Hernandez and collaborators, as well as the many students whom she thrives on mentoring, have done dozens of studies of the area’s ibis. They’ve banded, tracked, observed, and sampled hundreds of adults and juveniles from parks and compared them to Everglades birds. They’ve also raised nestlings in captivity for controlled studies and monitored ibis that dined at a local landfill.
These efforts proved Hernandez’s hunch: Local ibis are indeed gorging on lots of human food. They also move around less than birds that stay in natural areas, stick to feeding routines, and leave to breed earlier. What’s more, they are usually less stressed, as indicated by their hormone levels, and have fewer parasites, possibly because they spend less time looking for food and more time preening. On the other hand, not only do they tend to carry more salmonella—bacteria that can be dangerous to nestlings and people and a helpful proxy for the presence of other pathogens—but the diversity of healthy microbes in their guts was also lower. “The results point to the fact that there are some specific tradeoffs to using urbanized environments,” she says. “But what does that mean for the birds in the long term?”
Others are asking similar questions about the area’s other waders. Wood Storks were declared endangered in 1984, but since then have been rebounding due to careful conservation. This species, too, has recently started showing up in developed areas of South Florida. In a study published in 2020, Dale Gawlik, then at Florida Atlantic University, compared stork nestlings in the Everglades to those in urban colonies, such as one behind a car dealership. In years of plentiful natural food, storks in both areas fledged in similar numbers. But in a lean year when most nests failed in the Everglades, city birds consistently produced chicks (even though parents did sometimes feed them scavenged hot dogs and chicken wings).
Gawlik now views urbanized habitats as helpful “bet hedging” for the species’ conservation. “Urban areas are clearly not a substitute for natural wetlands,” he says. “But they may dampen the negative effects of bad breeding years. For a species that might live 15 or 20 years, cutting out five or six of those bad years could make a big difference.”
Many researchers, including Hernandez, want to better understand what makes individual animals bold enough to try out new foods, nest sites, or territory. Gawlik reasons that Wood Storks that survived the highest fever of Florida’s development boom in the 20th century may have had a stronger predilection for adapting to their new landscape. “They’ve essentially passed through this urban filter, and now they’re reproducing,” he says. If they in fact produce more nestlings, he speculates that genes conferring this advantage could be surging in the recovering population. In the race for survival of the fittest, a willingness to try a little junk food might not be such a handicap.
The three days I spend with Hernandez’s team are surreal and scary. It isn’t because of gators. While they work with White Ibis, hoarding toilet paper becomes sensible and elbow bumps no longer ironic. Our phones ping with urgent alerts, and I anxiously scan a headline about a sick JetBlue passenger who’d just traveled my flight route. Then the World Health Organization declares a global pandemic. On March 13, 2020, I fly home to quarantine just as COVID-19’s first wave unfolds.
During this time news stories speculate about the virus’s unknown origin. More than a year later, there is still no smoking gun, and controversy swirls around the question. But a strong possibility is that, like the deadly 2003 SARS outbreak that infected 8,000 people, and like many past pandemics, COVID-19’s source was zoonotic—the novel virus lived in animals before spilling over to infect people.
There’s a long history of pathogens from animals infecting people (and vice versa): avian influenza, Ebola, Lyme disease, and West Nile virus are just a few zoonotic diseases that worry public health experts today. There are more yet-unknown contagions with potential to jump between species. The more wildlife comes in contact with people and livestock, the greater the risk. As our growing global population pushes against the boundaries of degrading habitats, it’s become harder and harder to separate concerns about human, animal, and ecological health.
To contend with such hazards, a philosophy called One Health is gaining traction at the CDC, USDA, National Park Service, and other agencies around the world. It encourages, for instance, epidemiologists to care about deforestation in Brazil or livestock fairs in Ohio, veterinarians to monitor climate trends, and local wildlife and public health departments to work together to track diseases. The concept also guides Hernandez’s work: In towns where White Ibis gather for handouts, she wants to know about the implications for our health, too, not just theirs.
The reason is clear when we visit Indian Creek Park in Jupiter, Florida, where ibis poop coats the picnic tables. The birds, Hernandez has found, can harbor avian flu (which usually doesn’t directly infect humans but does pose spillover risk) as well as salmonella bacteria. Neither is too surprising for a wading bird. In 2006 scientists also had reported both pathogens, as well as Newcastle disease, in the urban Australian Ibis, adding to authorities’ motives to control its numbers and access to food and trash.
There’s no reason to think that either ibis species poses an unusual or high public health threat, she says—not much different than, say, Canada Geese whose excretions splatter lawns across the continent. But bigger picture, that’s not really the point. “When human activities lead to an ecological imbalance—the overabundance of birds in this case, which increases potential for contact between people and birds—it’s a numbers game in terms of the opportunity for zoonotic viruses or bacteria to infect people,” says Jonathan Epstein, author of the 2006 study and now vice president of science and outreach at the nonprofit EcoHealth Alliance.
Because many of Florida’s urban ibis also visit the Everglades, Hernandez worries any diseases they pick up could spread in wider avian populations. In April through July 2020, with the golf course (and greater world) in lockdown, Seixas tested its nestlings for salmonella, which she detected in most. She also sent four nestlings found dead for necropsies, and the results contained a surprise: Three were positive for West Nile virus.
“This was never reported in White Ibis nestlings before,” Seixas says. Yet neither she nor Hernandez can say exactly how concerning that is. It’s possible they commonly carry the virus, but no one had ever looked for it.
While breeding populations of White Ibis vary widely year to year, their numbers in the Everglades have trended sharply upward over the past three decades with improved water management. And in winter months in nearby Palm Beach County, the species has become the most common wading bird for the past 20 to 25 years, according to the annual Christmas Bird Count.
The count’s organizer, Chuck Weber, welcomes the ibis’s presence: “Because they are so beautiful, I think people relate to the birds and make a connection with nature.” Similarly, for now, Gawlik says it’s good if people see more Wood Storks where they live, if it generates support for the billions of dollars invested in Everglades restoration. “Here’s this threatened wetland bird that flies back and forth from natural marshes to urban areas,” he says. “It’s a chance for people to see that these wetlands are full of more than mosquitoes and alligators.”
But there is that fuzzy love-hate boundary. Frederick, the Everglades ecologist, notes that at first everyone gets excited if a Wood Stork colony pops up in a given subdivision, “but inside of a month they all hate it.” For any species, ecologists say there is a so-called cultural carrying capacity that varies by animal. Compared to Australian Ibis, White Ibis are quieter and smaller in stature, Hernandez notes—so they may be easier to tolerate, even if the birds become dumpster divers in much larger numbers than today.
Hernandez believes White Ibis are far less likely than Australian Ibis to ever nest en masse within Florida’s golf courses and housing developments, as long as healthy habitat in the Everglades endures. But give the bird a few more decades to adapt to cities that have encroached on its turf, and such a future is possible—and that would mark “a real sea change” in the birds’ ecology, Frederick says. If the population as a whole became more sedentary and supported by human handouts, it might be stable, but those awe-inspiring “boom” years could disappear. In this scenario, Hernandez fears that even White Ibis could exceed our tolerance and become a pest to control. To forestall that fate, she thinks more public education to discourage people feeding them would go a long way.
Along with White Ibis, an estimated 20 percent of the world’s bird species occur in urbanized areas, a majority of which are native species. While some are declining, others adapt or even exploit opportunities in city landscapes. Many are changing their behavior to do so: nesting on bridges rather than cliffs, singing at higher frequencies to be heard over traffic, breeding at odd times. Some landfill-feeding White Storks in Spain have stopped their famed migrations.
But for every bird that does well enough in this terrain, many specialized, sensitive, or shy species simply can’t or won’t. Evolved over millennia, they live in habitat niches, consume waning food resources, or require open, unfragmented spaces. Some decline too rapidly to adjust to new pressures. For them, human-dominated lands, urban or rural, may never be a helpful hedge for survival.
Across the world, the wildlife mix is changing, headed toward clear “winners” and loss of biodiversity overall. Florida would lose its essential character without the full range of species that rely on the River of Grass. In cold evolutionary math, White Ibis may do fine. Possibly they’ll thrive. But if that were the story’s end, we would all lose out.