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20 Years, 40,000 Birds: How One Small Scientific Station Has Tracked South Florida's Migrating Birds

Michelle Davis, who runs the Cape Florida Banding Station, holds a common yellow-throat warbler and a bag in her other hand.
Federico Acevedo
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Tropical Audubon
Michelle Davis, who runs the Cape Florida Banding Station, holds a common yellow-throat warbler. The bird will be examined to determine its sex, age and weight before being outfitted with a metal band on its leg to track its movements.

This post was updated Monday, June 7.

Every spring and fall, South Florida becomes part of one of the planet’s most amazing spectacles: the seasonal migration of billions of birds.

Birds migrating from as far as South America and Greenland fly up and down the Atlantic flyway, crossing Florida as they make their to and from northern breeding grounds. Some, like the tiny blackpoll warbler, can fly nonstop for three days, crossing the ocean in a single flight. Others fly at night, taking advantage of the dark to hide from predators, when the air is cooler and calmer.

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For the last two decades, their comings and goings in South Florida have been tracked at the Cape Florida Banding Station, thanks largely to the efforts of a single scientist.

“It was a small operation and on a shoestring budget, if a budget at all,” Michelle Davis said, of founding the bird banding station in 2002. At the time, she was working as a field biologist at Everglades National Park.

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Federico Acevedo
An American redstart is among the birds banded at the Cape Florida Banding Station. Redstarts travel thousands of miles every year from North America to winter in Mexico and Central America.

Two decades later, that side gig has turned into one of the longest data sets for migrating birds from South Florida. Davis and a small band of volunteers have examined, weighed, measured and banded nearly 40,000 birds.

“Michelle Davis has been like a superhero,” said Tropical Audubon Society executive director Paola Ferreira. “It is an amazing effort that she's done on a shoestring budget and what they have accomplished is just huge.”

Members of the nonprofit have helped out the banding station for years, Ferreira said. But when money got tight — the pandemic hit and Davis nearly had to shut down the station — Tropical stepped in and made it part of the organization’s official mission.

“It would be sinful to let the station not continue collecting these data,” Ferreira said. “We have 20 years of data and 20 years from now, when neither Michelle or us are here, we want the station to continue their amazing work.”

Banding Birds Goes Back Centuries

Birds have been used for centuries to carry messages. Romans tied knotted threads to the legs of swallows to send messages, the American Ornithological Society reported in its journal, The Auk, in 1945. Early falconers often banded birds to identify the owners. In the late 1800s, banding spread across Europe as ornithologists discovered tracking movements could provide a trove of information.

In the early 1900s, U.S. government scientists began banding birds, including a flock of black-crowned night herons near Washington with tags labelled “Return to the Smithsonian Institution.” One of the birds was later discovered in Cuba, the first long-distance traveler recorded, according to The Auk.

In the 1920s, North America collected the scattered bird banding organizations under the Bird Banding Laboratory to be run by the U.S. Geological Society and the Canadian Wildlife Service.

Technology has provided far more advanced methods of tracking with satellites, radio tags and modeling. Even weather radar can pick up migrating birds. Citizen scientists have also jumped in, using social media and sites like eBird to collect information.

pvc weighing birds.jpg
Federico Acevedo
To weigh the birds, they are placed head first into PVC pipes, that help keep them from being injured.

A handful of old-school banding stations remain along the Atlantics coast, from North Carolina to Florida, where tiny numbered metal tags issued and tracked by the government are attached to a bird’s leg. But only three, including Davis’, have consistently stayed open.

“They've banded more than 114 different species and on average 1,900 birds get banded annually during the fall,” Ferreira said. “So if you just imagine where this station is located, it just gives me chills.”

That’s because the station is tucked into Bill Baggs State Park, in an area that was bulldozed in the 1950s to make way for hotels, condos and homes. It ended up becoming the park, instead, overgrown with invasive Australian pines that provide little of what birds need. After Hurricane Andrew knocked over many of the pines, Miami-Dade County and volunteers restored the tropical hammock with strangler figs, cabbage palm, pigeon plum and a jungle of trees birds love.

“It's uniquely located in a very urbanized community. And what the data and just those staggering numbers — 1,900 birds in just the fall migration — tells you is just the importance of Bill Baggs being located there,” Ferreira said.

Behind The Scenes Of The Banding Operation

Davis runs the station with a merry band of volunteers: an artist who works as a naturalist, a sound engineer, a doctoral student, hardcore birders and anyone she can convince to spend a morning looking for birds.

black and white warbler.jpg
Federico Acevedo
Black-and-white warblers are among the migrating birds banded at the Cape Florida station.

The banding operation itself is pretty low key: just a wooden platform under a tent hidden in the woods. A folding table holds rudimentary tools needed to inspect and band the birds: a metal ruler, a scale, and PVC pipe in different sizes to hold birds when they’re weighed. The numbered bands are lined up on a board, like ring sizers at a jeweler.

“They're issued by the U.S. government. They sign them out and you have to have a permit,” Davis said. “You have to kind of apprentice with another bander and then have a reason. And you get issued these bands for different-sized birds. I have bands for Blue-gray Gnatcatchers. The biggest band I have [would fit] a red-shouldered hawk.”

The bands can last for years.

“The oldest wild banded bird is Wisdom, the albatross. She’s 70,” Davis said. “I think they may have had to replace her band once.”

Having the station on Cape Florida provides really important information about birds because it’s such a critical stop for migrating birds who’ve burned up much of their fat on long-distance ocean crossings.

“It's such an obvious geographic funnel for birds going north and south to travel up and down the Florida peninsula,” Davis said. “This is what they call a migrant trap or stopover habitat. It’s like that one gas station in the middle of Alligator Alley. If you're getting low, that sucker better be open. “

While more sophisticated ways of studying bird behavior exist, Davis said banding still provides critical information that eBird and larger scale observations don’t provide, like sex and age and weight. That kind of information can reveal what’s happening to birds over time — if numbers are beginning to shrink or migration patterns are changing because climate change is increasing temperatures or altering plants the birds need to survive. That, in turn, can expose changes in habitat.

In April, data collected on migration patterns showed that rising temperatures driving the earlier arrival of spring in North America was throwing off migrations for birds that travel the farthest to breeding grounds. That’s helping scientists identify birds that may be more vulnerable to a warming planet.

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Fewer than a dozen bird banding stations track migrating birds along the southeast Atlantic coast. Only three have been operated consistently.

To catch the birds, Davis strings the nets under trees with berries, like ficus. The nets are only up when someone is manning the station and they get checked every 20 minutes.

“Imagine a volleyball net except with thread and not string and the birds don't see the net and they fly into it,” she said.

Davis and the volunteers take their time untangling the birds from the nets so they don’t get hurt. Then they slip them into a drawstring bag, where the birds quickly calm down. Over the years, Davis has collected dozens of bags, that either she made or volunteers made for her, from old sheets or shirts. One bag was made from boxers that belonged to a volunteer’s husband.

Once the birds are out of the bag, the work is fast. They get weighed, measured and examined.

For the last two seasons, Steffanie Munguia has helped Davis give their birds their physicals. She was trained in ornithology and is now working on a PhD at Florida International University. To assess the birds, she blows on their belly feathers to reveal their chests.

“We're looking at their pectoral muscles, which are the muscles to help them fly. We're also checking their fat,” she said. “Migrating birds tend to have more fat on them and are a little bit chunkier than some of the other guys. Most of our warblers that are passing through are in migrating condition.”

Roxanne Featherly, an avid birder and friend of Davis’, said helping out at the banding station has given her a whole new way to appreciate them.

“It's such a big difference when you see the bird with your binoculars and then when you're actually holding it in your hand,” Featherly said. “You see all the detail of the feathers and the feather groups and the bill and you're like, 'Oh, I didn't know that had such a long, sharp bill.'”

'Something Always Draws Me Back'

As a kid, Davis said she loved to draw birds. She still does. At the University of California Santa Cruz, she was torn between studying art or biology. UC Santa Cruz offers one of the country’s leading degrees in science illustration. Davis ended up doing both when she found a professor who needed a field illustrator. She says that was back in the golden age of field work.

A northern cardinal.
Tropical Audubon
Marc Kramer

“Science kind of has trends. And this whole migration ecology was really popular in the '90s so there was a lot of jobs,” she said.

Now, the jobs are less plentiful and the pay was never great.

“I don't get rich, but I did get enough money together to buy a house at the bottom of the market. So I've been lucky enough to make it a job,” she said. “It is compulsive for me. Every time I tried to leave field work — I was a waitress, I worked in a warehouse, I work at my office job — something always draws me back into doing field work.”

Of all the changes she’s witnessed over the years, she said what stands out is the plummeting number of birds.

“When I first started in the '90s, the old timers would be like, 'Oh, yeah, back in the '60s, every time you had the right kind of weather, you would have hundreds of birds. There would be birds everywhere,'” Davis said. “Now I'm the old-timer. It’s like, ‘Remember 30 years ago?’"

You can still find a variety a birds, Davis said, just not nearly as many.

Due to incorrect information supplied to WLRN, an earlier version of this story misstated the number of birds banded every year. It is 1,900. An earlier version also misidentified Blue-gray Gnatcatchers and strangler figs.