Hana Weaver feeds a Sharp-shinned Hawk that hatched at the Peregrine's Fund Propagation House in Ponce, PR. Photo: Erika P. Rodriguez

Conservation

Hurricane Maria Almost Wiped Out These Hawks. Can We Save Them Before the Next Big Storm?

Scientists are in a race to bring the Puerto Rican Sharp-shinned Hawk back from the edge of extinction, one hand-reared chick at a time.

Hana Weaver hasn’t left the house in weeks. She’s living just 20 minutes from town and less than an hour from the beach, but she hasn’t gone hiking or swimming since mid-April. She hasn’t slept through the night in all that time, either. Every two to three hours or so, she wakes up without an alarm, unable to go back to sleep until she checks on the eggs incubating in the next room of a one-story house perched on a forested mountain north of Ponce, Puerto Rico.

Her vigilance is about to pay off. On this May afternoon, the first Puerto Rican Sharp-shinned Hawk egg of the season is hatching.

The biologist flips a blonde braid over one shoulder and washes her hands like a surgeon, scrubbing brown iodine soap between each finger, around her hands, and up to her elbows. Inside a white-walled room, she pulls on a pair of synthetic rubber gloves and peers through an incubator window at three eggs, all pulled from the same wild nest. They’ve all “pipped,” she explains, pointing to the hairline fractures that indicate a chick has started the days-long hatching process. One egg also has a large puncture. As we watch, the black tip of a tiny beak busts through the hole, wiggles to widen it slightly, and then retreats back inside.

Weaver observes the first egg of the 2019 season beginning to hatch. Photo: Erika P. Rodriguez

These eggs, 12 in all, are hatching in a sterile room instead of a wild nest as part of a two-year-old rescue mission. The birds are a subspecies of the North American Sharp-shinned Hawk. They live only in Puerto Rico, and like many raptors in the Caribbean, habitat loss, nest predation, and parasites have ravaged their populations for decades. Now the birds face another menace: Climate change threatens to bring more forest-flattening storms to the region. In 2017, Hurricane Maria delivered a near-fatal blow, killing nearly 75 percent of the known population of remaining sharp-shins. To protect the hawks when they’re most vulnerable, Weaver’s team is raising the helpless chicks in captivity and then releasing them as hardy fledglings.

After nearly 40 minutes, the egg lurches and, in one quick motion, something slimy and pink lunges out of the top, then topples over. For a moment, the hatchling rests face down on the white mesh. Small enough to fit in the palm of my hand, it looks like a miniature raw chicken, except for the teeny talons and raptor’s killer beak. 

“Aw, guys, our first baby!” Weaver says as she and two colleagues who also live in the house huddle around the incubator, cooing in awe at this new life they’ve shepherded into the world. Weaver’s sleep schedule is about to become even more precarious, as she must check on the brooder around the clock. Soon she’ll be feeding this chick and the other hatchlings every four hours during the day to build up their strength before setting them free. It’s a perilous bet, but one that offers the population its best chance at survival.

Much like its North American relatives, the Puerto Rican Sharp-shinned Hawk, or Gavilán de Sierra, avoids people, nesting in mature forests in the island’s tallest mountains. The russet-brown and slate-gray birds have short wings and long tails ideal for navigating around branches and hunting Bananaquits and other small birds. It’s nearly impossible to find these secretive hawks outside of breeding season, when males perform their aerial ritual, hovering above the forest and dipping up and down, up and down, signaling their territory to potential mates. From January through April, as the hawks start courting and nest building, Weaver and her team wake before dawn and watch the treetops from highways carved into the side of the Cordillera Central mountain range. When they spot a black dot bobbing above the canopy, they approximate its GPS coordinates and then plunge into the forest to try and find the nest. 

The Puerto Rican Sharp-shinned Hawk has been declining for at least 40 years, its demise driven largely by reproductive threats. Bot flies burrow into nestlings’ skin and sap their nutrition and energy, eventually killing them. Predators like Red-tailed Hawks and Pearly-eyed Thrashers make quick meals out of eggs and young chicks (and, in the case of red-tails, sometimes the parents, too). Meanwhile, humans have increasingly encroached on the bird’s forest habitat. 

In the 1980s, when scientists first surveyed this species, sharp-shin populations hovered around 240 individuals. In just seven years, that number dropped 40 percent to 150, prompting the U.S. Fish and Wildlife Service to list the Puerto Rican Sharp-shinned Hawk as endangered in 1994. The FWS wrote a recovery plan, but no one took action for two decades.

Weaver listens (top) to an egg that is not showing development. If the egg is still alive, she can hear the embryo moving inside. Weaver marks the third Puerto Rican Sharp-shinned Hawk hatchling (bottom) with orange marker. She marks each hatchling with a unique color so she can keep track of them and monitor their growth. Photos: Erika P. Rodriguez

But In 2011, Julio Gallardo, then a Ph.D. student at Mississippi State University, started looking for sharp-shins as part of a study connected to another endangered species, the Puerto Rican Parrot. He found so few sharpies that he contacted the Peregrine Fund, a U.S.-based raptor nonprofit that works internationally.

Peregrine Fund biologist Russell Thorstrom, Gallardo, and a couple of international volunteers began surveying the sharp-shin population in 2015, monitoring nests and banding birds in three forest reserves. By early 2017 they’d tracked down 75 hawks in five reserves. Everything changed that September. Hurricanes Irma and Maria tore through the island in quick succession, flattening forests and triggering landslides that reshaped the mountains themselves. When Thorstrom and Gallardo returned in 2018 to survey the post-storm wreckage, they found just 19 adults.

That’s when they called in Weaver to develop and run the first-ever captive propagation program for Puerto Rican Sharp-shinned Hawks. She was a natural choice for the project, says Thorstrom. At the time, Weaver was working with California Condors for the Peregrine Fund. Her experience with raptors started much earlier. Weaver grew up on a New Mexican ranch hand-rearing Peregrine and Taita Falcons with her father, Jim Weaver, a Peregrine Fund founder. He taught her how to carry an egg gingerly (like trying to keep an ice cube in the middle of a cup of water), how to hold a newly hatched chick, and how to cut a cowbird into pieces small enough to feed a raptor hatchling. Weaver knew that hawks in the Accipiter group, like sharp-shins, develop faster and can be more high-strung than other raptors, so she relied heavily on advice from Peregrine Fund veterans and numerous falconers when she started the captive-rearing project in 2018.

The first days of a sharp-shin chick's life. Birds hatch with their eyes open. By the second or third day they're can peck at food above them, and their long white down comes in at about one week. Video: Erika P. Rodriguez

That spring, Thorstrom, Gallardo, and their crew collected eggs for Weaver from three of the six nests they found. Only two of the wild-hatched chicks fledged, even though the scientists augmented the parents’ hauls with Shiny Cowbirds and Coturnix Quail. Meanwhile, Weaver reared and released chicks from six of the eight eggs in her care.

The project’s immediate aim is to restore the wild sharp-shin population to its pre-Hurricane Maria levels. Once the scientists tally at least 75 hawks across three forest reserves, they’ll likely scale back captive breeding activities while continuing to monitor and support wild nests, says Thorstrom. They’ll achieve this goal in the next 5 to 10 years, he estimates, provided no catastrophic storms hit the island in the meantime.

This spring the team counted 18 nesting adults. They monitored four nests, leaving the parents to tend the eggs, and removed all 12 eggs from four other nests—and added a new element to their research. At two nests in the Maricao State Forest, they left behind dummy eggs; they planned to replace those with 7- to 10-day-old captive-hatched chicks from the neighboring Toro Negro State Forest, to boost local genetic diversity and skip the most vulnerable stages of chick development. The rest of the chicks will return to the wild when they’re ready to fledge, at about four weeks.

That means that by mid-May Weaver is only about halfway through her self-imposed house arrest. The rest of the team, meanwhile, sets out into the forest every day before sunrise, keeping watch over the free-flying flock. 

The team tracks nest success in the wild and the progress of eggs brought into captivity on a white board (top). Weaver (bottom) cuts up Shiny Cowbird to feet recently hatched chicks at the field house. Photos: Erika P. Rodriguez

At 6:30 one morning, I set out with Jaime A. Botet, a Puerto Rican and one of the project’s field biologists, to check on a hawk pair that’s got the team worried. The duo has eggs, but lately the female hasn’t seemed attentive enough to the nest and the male hasn’t seemed attentive enough to the female. They’re nesting in a pocket of mature forest that survived the hurricane, but to reach them we have to traverse slopes cloaked in dense vegetation and studded with reedy palm trees that colonized these slopes after Maria stripped them bare. Botet hikes quickly and confidently. I stumble behind him, tripping over bamboo vines and grabbing onto thorny tree trunks.

After almost an hour, we reach a tree marked with a pink ribbon. The canopy is much denser here, the trees larger, the ground clearer of weedy vegetation. Botet circles the tree for several minutes, trying to spy the nest—a jumble of sticks mostly obscured by waxy green leaves 20 feet up. We settle down on a patch of dirt to wait and watch. At this point in the breeding season, Botet and the other team members—Michaela Gustafson and Daniel Erickson—visit each of the 11 nest sites every few days, writing down everything that happens, or doesn’t, during a four-hour period.

If we don’t spot the adults, Gustafson will climb up for a closer look. An avid rock climber, she’s the team’s designated tree climber. Gustafson goes up only when necessary: to collect eggs, spray a nest with insecticide to kill bot flies, temporarily remove wild chicks for banding, or check if something seems wrong. 

Botet is the first Puerto Rican to work on the project. Like many locals, he didn’t know about the critical status of the hawk before he applied for this job. But he’s proud to be working with a species unique to his island, and he’s started spearheading more outreach for the project, such as talking to radio stations and at high schools to raise awareness of the bird’s plight and encourage others to take part in conserving it. People can advocate for protecting forests, for instance, or maintain hawk habitat on their properties.

For Botet, Hurricane Maria highlighted the importance of Puerto Ricans fighting for Puerto Rican wildlife. “I definitely feel an urgency to work with wildlife after the hurricane,” he says. “They can’t speak for themselves; they don’t have a voice.”

Fog rolls over the mountain as we wait. Eventually, the female appears, visits the nest, then flies off again, calling out for food. But when the male appears, its talons are empty. During nesting season, females incubate the eggs while males hunt. Hungry females will occasionally attack their mates, a behavior not entirely unheard of in the raptor world, where females are, on average, twice the size of their male counterparts. Apparently this female isn’t ready to turn to violence, but it’s obvious that she isn’t pleased. She lands on a nearby branch and spreads her tail and wings in an aggressive stance, shrieking in the direction of the male. Then she flies back to the nest, and the male flies off, presumably to hunt. 

A downpour thwarts our plan to see if the male returns with food. The birds aren’t active in the rain, Botet says. He leads the way back up the creek, as I stagger behind him. 

Navigating these mountains was treacherous in a different way last year, when downed trees blocked access to nest sites, says Melissa Murillo, who has worked on the project intermittently since 2016 and became the field coordinator this summer. In early 2018, she conducted surveys with Gallardo and Thorstrom and helped train Weaver. She’d planned to stay for three weeks; she stayed for three and a half months. “It felt like what it would look like to an ant when a lawn mower comes through,” Murillo says. “All the trees were snapped.”

A Category 4 storm when it reached Puerto Rico, Maria dumped up to three feet of rain, triggering widespread flooding and landslides that reshaped the topography of the mountains. Winds of 130-plus miles per hour whipped trees, yanked the roofs off houses, damaged cell phone towers, and pushed over powerlines, cutting electricity to all 3 million people on the island. While estimates range widely, the official Puerto Rican government death toll is 2,975 people.

Whitewash from a hawk near a nesting site at Toro Negro Forest (top). Michaela Gustafson observes the nest (bottom). Photos: Erika P. Rodriguez

The wreckage is less visible today, with palm trees and dense understory inhabiting what was, a year ago, a flattened forest. Sharp-shins, however, can’t use this vegetation. They depend on tall trees and dense canopies to build and camouflage their nests. An estimated 30 million trees were killed or damaged during the hurricane, and large trees fared particularly badly, says Maria Uriarte, a Columbia University ecologist who has studied Puerto Rican forests since 2002. “The damage was incredible,” says Uriarte. “I had never seen this type of event before.”

It could take decades for those big trees, like the leche prieta so many hawks prefer, to grow back. If the next big storm hits sooner rather than later, the recovery could take even longer. So far this year, Puerto Rico has experienced heavy rains from tropical storms, but no direct hits from a hurricane.

Stronger storms and hurricanes will threaten Puerto Rico in coming years as we continue to pump more carbon dioxide and other greenhouse gases into the atmosphere, causing global temperatures to rise. This July, for example, was the hottest month on record. Warm air holds more moisture, creating ideal conditions for monstrous tropical storms and hurricanes to form in the Atlantic Ocean. While we don’t yet know if climate change will spur more hurricanes overall, it will almost certainly generate more severe Category 4 and 5 hurricanes, according to the National Climate Assessment.

These hurricanes will dump more rain; Hurricane Maria brought more rainfall to Puerto Rico than any other hurricane since 1956, due at least in part to global warming, according to a study published this year in the journal Geophysical Research Letters. What’s more, with rising sea levels, storm surge will be higher. And trees that survive the high winds could still be knocked down at the roots by flood-induced landslides.

If the aftermath of Maria is any indication, recovery from future storms and extreme weather events is unlikely to be swift or easy. It took the Puerto Rico Electric Power Authority 11 months to fully restore electricity, and it still goes out from time to time. About 30,000 people still live under blue tarps instead of roofs, NPR reports. The U.S. government estimated the storm caused $91 billion worth of damage, and Congress approved sending $42 billion. As of May, only about $14 billion had been sent to the island, the Washington Post reported. President Trump has adamantly and vocally opposed sending more aid to Puerto Rico. This summer he placed restrictions on about $8.3 billion in federal disaster mitigation while the island grappled with a political crisis that led to widespread protests and the eventual ousting of Puerto Rico’s governor. It’s unclear when Puerto Rico will see that financial support.

Gustafson (right) and Botet give Weaver updates on the nesting sites they're monitoring. Photo: Erika P. Rodriguez

Funding for the island’s many endangered species has also been in short supply. Though the FWS allotted $11 million to shore up its captive breeding efforts for the Puerto Rican Parrot after Maria, it provided just $100,000 for the sharp-shin captive breeding program in 2018—the first time the program received federal funding at all. The Peregrine Fund raised another $110,000 itself to keep the project going. As is the case in the rest of the United States, there simply aren’t enough federal resources allotted for conserving every endangered species on the island, so NGOs often step in to fill the gaps, says Nilda M. Jimenez Marrero, the endangered species coordinator for the country’s Department of Natural and Environmental Resources.

As for safeguarding sharp-shins, the Peregrine Fund has played a critical role, says Marrero, providing the on-the-ground support her agency cannot. Without Thorstrom, Weaver, Botet, and the others, the birds might have slipped into oblivion without anyone noticing. 

Botet and I return from our hike sopping wet and head straight for the chicks. All three in the hatcher have broken free from their shells by now, and now they’re nuzzled together in a nest of white hand towels. Each has a soft layer of white, downy fuzz framing curious black eyes and tiny, open beaks.

When Weaver pulls the makeshift nest out of the brooder, the oldest chick opens its beak expectantly, head lolling back on its long neck at an awkward angle. Definitely a female, Weaver determines; it’s much larger than the other two chicks.

She carefully scoops up the chick from behind, letting it shuffle backward into the palm of her hand, and then deposits it in a shallow orange disc used for feeding and weighing hatchlings. With tweezers she picks up a tiny morsel of a bloody paste made from finely chopped Shiny Cowbird. As soon as she makes a soft “cheep cheep cheep” sound, the chick waves its head about wildly, flailing as it attempts to grab the food. When beak and meat finally connect, the chick furiously opens and closes its mouth and waggles its tongue to swallow. Then it looks around expectantly for its next bite. “They’re already getting stronger!” Weaver says.

When the chicks are a couple weeks old, Weaver will finally leave the house. The entire field team will decamp to a cabin about an hour away and transfer the chicks, each sporting unique identification bands on their legs, to an elevated platform covered in branches to imitate a real nest in a real tree. For three months, the biologists will monitor the birds as they eat food zip-tied to the platform and learn to use their wings. Just before the young hawks fledge, the scientists will glue trackers to their outer feathers, allowing them to follow their movements in their first free-flying days. Soon, however, the gadgets will fall off, and the hawks will disappear into the forest.

Because the population is so small, each egg, chick, and adult holds potential for the survival of the species itself. Not everything went according to plan this year. Three of the eggs failed to hatch. The effort to foster three chicks with a pair of adults in the Maricao State Forest didn’t pan out: After the female started overfeeding the little birds and accidentally pushed two out of the nest, the team rescued one chick from the nest and one from the forest floor and brought them back inside for their safety. And the duo Botet and I visited didn’t hatch any chicks.

There were successes, too. In the wild, three pairs fledged seven healthy chicks after the biologists treated two nests for bot flies. And at the elevated platform, as the eight captive-raised chicks were starting to fledge, an unexpected visitor arrived. A female hawk that Weaver released the year before returned and took over guardianship duties from the humans. She acted as a surrogate parent, protecting the young brood from Red-tailed Hawks lurking nearby. The humans watched from below as one generation of these highly endangered birds helped the next make it into the wild. In the forests of central Puerto Rico, these birds will then try to raise future generations of their own—hopefully before the next storm arrives. 

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