High in the baby-blue sky above Curry Hammock State Park in the Florida Keys, a very small merlin falcon with a very big attitude repeatedly attacked an osprey five times its size.

“Look, it’s pecking the osprey,” said Luis Gles, binoculars pointed up at a 30-degree angle to the battleground 100 feet above us. “They are scared of nobody, they attack even peregrine falcons.”

The merlin wheeled, darted and dove again on the osprey. Then the two birds broke off hostilities; the merlin to continue its migration to its wintering grounds far to the south and the osprey to hunt for a fish dinner.

“When I arrived, I was in love with peregrine falcons,” said Gles, a native of Colombia who now lives in Miami. “But merlins stole my heart.”

The temperature was fast climbing to 90 degrees on this shirt-soaking humid day in late September. Gles stood in the sun on the second-floor observation deck of the building that houses the park’s bathrooms. He searched the skies for migrating raptors — birds of prey, a group that includes falcons, hawks, ospreys, eagles and kites — as they soared, flapped and glided past on their months-long journey to their winter homes in the Caribbean as well as Central and South America.

Gles and two other experienced birders had been hired by the Florida Keys Audubon Society to count raptors as part of the Florida Keys Hawkwatch, an annual census of migrating birds of prey. For the past 12 years, Curry Hammock State Park on Little Crawl Key has hosted this Hawkwatch, one of more than 100 fall ones conducted around the country in collaboration with the Hawk Migration Association of North America.

In the late summer and fall, tens of thousands of raptors fly over the Keys as they journey way south from their breeding grounds in Canada and the northeastern United States. Because raptors prefer not to fly over large bodies of water, the Keys act as a natural funnel, compressing the migrating raptors into a single concentrated stream of birds that fly over Curry Hammock State Park and on to the Lower Keys, where they muster the courage to cross the Florida Straits to Cuba.

But for some it is here, above this tiny key halfway between Key Largo and Key West, that they make their move south.

“This is the shortcut,” Gles said. “It’s 80 miles to Cuba, closer than Key West.”

With the migrating birds come flocks of birders. Curry Hammock in the fall is one of the few places in the world where a birder can expect to see migrating peregrines. “I guarantee it,” Gles said.

His confidence was not misplaced. Counters here logged 1,506 peregrines on Oct. 10, 2015, the highest daily count ever recorded anywhere in the world. This season, a total of 3,588 peregrines were spotted, including 500 on Oct. 13. When this year’s count ended on Oct. 31, 19,067 raptors of all species had been tallied — an average of 46 birds an hour over the two-month Keys Hawkwatch.

Watchers keep spare pairs of high-power binoculars for visitors to use. If a bird lands, people may use the team’s more powerful spotting scopes.

“Visitors are absolutely welcome at the Hawkwatch,” said Chris Payne, a native of Somerset, N.J., who is a member of the counting team and a lifelong birder. “Engaging guests is a crucial part of our work because increasing public interest is the best way to ensure that the raptors we observe are protected for future generations.”

Starting the count

“There’s a peregrine,” Gles said.

Above us a fast-moving bird with a fighter-plane profile was making a beeline south for Cuba. “It’s migrating. You can tell by the height.”

He shifted his binoculars to slightly to the right.

“Looks like another peregrine. Adult. Okay, it’s streaming” — flying fast, a telltale sign that it’s migrating.

Spotters only counted southbound migrating birds. It was sometimes hard to tell migrants from residents. Several ospreys make their permanent home in the Middle Keys. Counters don’t record an osprey until it makes its move south.

A dozen small birds flashed by and headed over the water. “Barn swallows. They’re heading straight to Cuba,” said Lindsey Duval, of Saratoga Springs, N.Y., the third member of the counting team.

Duval entered the barn swallows in a separate notebook that records non-raptor sightings. A glance at its pages revealed a menagerie of birds that could have been named by Dr. Seuss: worm-eating warblers, short-billed dowitchers, lesser yellowlegs, northern parulas and yellow-billed cuckoos.

“We count every bird,” Payne said. One team member acts as the official counter, the others as spotters. Every hour, the counter recorded the number and kind of raptors that were seen in the previous hour. At the end of the day, daily totals for each species were uploaded to Hawkcount.org. Non-raptor counts were uploaded to Ebird.org, the website maintained by the Cornell University Lab of Ornithology. The counts help researchers monitor bird populations.

Peregrines are the star attraction at the Florida Keys Hawkwatch. Their name derives from “peregrinus,” which means “wanderer” or “foreigner” in Latin. Falconers prize female peregrines; particularly able hunters can fetch up to $25,000 in the bird bazaars of the Middle East.

These crow-size birds cruise at 20-to-50 mph but can reach more than 200 miles an hour in a “stoop” — their characteristic hunting dive. (Fun raptor fact: Peregrines can ball up their feet into fists when they dive and literally KO a small bird out of the sky.)

“I’ve got another peregrine,” Gles said. “Fingers. Two glasses up. . . . No, no, no. It’s a merlin.”

Most sightings were measured in seconds, a test of a birder’s eyesight and identification skills. To meet the challenge, spotters here spoke in a cryptic code passed down from one team of hawkwatchers to the next.

Spotters called out the bird’s altitude in “glasses” — how many viewing planes up from the horizon the bird is flying. A call of two glasses told spotters to lift their binoculars two planes up from the horizon, or roughly 30 degrees.

They also called out a landmark over which the bird is flying. In this flat landscape, the reference points were nearby trees and power poles. Two buttonwood trees with crowns that poked above the scrub were “Big Bob” and “Little Bob.” A cluster of dead, leafless trees was “the Fingers.”

Spotting the birds is only the first step. Identifying these fast-flying birds is a bigger challenge, even for experienced birders.

“For falcons, the best indicator is their wing shape — they have very pointy wings,” Payne said. By contrast, hawks have broad wings with feathers that extend like fingers from the wingtips.

Size is another tipoff. “The peregrine is our largest falcon,” Payne said. “They are much larger and chunkier as opposed to the kestrel, the smallest of the three species.”

Spotters scrutinize how the birds flap their wings. “The peregrine has a big, powerful flap that comes right from the base of the wing,” Payne said. “Merlins are like Energizer bunnies; they just flap like crazy. And kestrels, if you take a banana peel and flap it up and down, it looks like a kestrel flapping — real loose and floppy.”

Into overtime

It was approaching 4:30 in the afternoon. The counting team had added a half-hour to its regular day to try to spot another osprey, which would bring the total count of the birds to 1,600 for September.

“There, up high,” Jeff Payne, Chris’s father, said as the day’s last osprey angled southward toward Cuba.

The count was over for the day. Chris Payne sat cross-legged in front of a well-used white tally board that listed raptor species. He erased yesterday’s count and enters today’s numbers: 47 peregrine falcons, 37 ospreys, 25 merlins, 11 broad-winged hawks, six northern harriers and a handful of other raptors — a total of 136 birds in all, including the day’s prize, a rare short-tailed hawk.

“It is hard to appreciate the sheer bulk of birds that move through a single area each fall without seeing it yourself, day after day, for a whole season,” Payne said later, marveling at the Florida Keys Hawkwatch experience. “Personally, the variety of raptor species and number of peregrine falcons are what sets FKH above other hawkwatches for me.”

Morin is a writer based in the District. Find him on Twitter: @richmorin.

More from Travel:

If you go

Where to stay

Tranquility Bay Beach House Resort

2600 Overseas Hwy.


This luxury resort hotel and spa on the bayside of Marathon offers all the amenities at a reasonable price if you book during September and October before the winter rush.

From $169 for a standard room with two twin beds.

Captain Pip’s Marina & Hideaway

1410 Overseas Hwy.


Ernest Hemingway, Elizabeth Taylor and Jimmy Hoffa slept here. This older but fully renovated Keys landmark offers your choice of immaculate motel-style guest rooms, efficiencies or apartments with one and two bedrooms. From $190 for a ground-floor guest room with two double beds.

Hampton Inn

13351 Overseas Hwy.


Virtually every major motel chain is represented in Marathon and the Middle Keys. This Hampton Inn is the closest to Curry Hammock State Park. From $184 for a standard room with one king bed.

Where to eat

Butterfly Cafe

2600 Overseas Hwy.


Located in the Tranquility Bay Resort, this upscale and pricey restaurant is generally regarded as the best in Marathon. Panko-crusted grouper ($39) and the yellowtail snapper ($38) are reliably delicious but the Baja scallop risotto with piquillo pepper cream ($45) is the showstopper here. Ask for a table outside on the covered patio.

Florida Keys Steak and Lobster House

3660 Overseas Hwy.


Fish lovers, meat eaters and vegetarians can all find something to like at this informal but high-quality eatery. A simple and simply delicious broiled Florida lobster tail is priced at $27.95 (be forewarned: it’s just the tail; Florida lobsters don’t have claws). A prime Kurobuta pork loin chop cost $34.95 while non-meat eaters can enjoy zucchini meatballs over pasta ($21.95).

Stout’s Restaurant

8349 Overseas Hwy.


Where the locals have breakfast (and lunch). This diner, hidden at the end of a strip mall, has been serving up tasty breakfast and lunch classics since 1964. It’s hard to spend more than $10 here unless you splurge on the homemade lemonade ($3.50), but please do. No dinner service.

What to do

Curry Hammock State Park

56200 Overseas Hwy.


Take a break from the birds and walk along a mile-and-a-half nature trail through a tropical hardwood hammock with the largest populations of thatch palms in the United States. Rent a kayak, swim, and snorkel or lounge under a palm by the sandy beach and watch kite-boarders soar into the sky (and, too often, crash down with a splash). The park’s 28 campsites for tents and RVs have water, electric, picnic tables and fire pits. Admission to the park is $4.50 for one person and $5.50 for two or more.

From early September through early November, experienced birders take up their positions at 9 a.m. to 4 p.m. daily on the second-floor deck of the building housing the bathrooms at Curry Hammock State Park. These bird-counting pros can answer questions from visitors and have extra binoculars to loan. Visiting birders are welcome to join in the count, though a member of the official hawkwatching crew must confirm any sighting.

Turtle Hospital

2396 Overseas Hwy.


Injured sea turtles are rehabilitated and returned to the wild here. The staff offers educational programs and a tour of the hospital daily every hour on the hour from 9 a.m. to 4 p.m. Reserve a place on a tour at least a day in advance as they fill up fast. $25 for adults and $12 for children 4 to 12 years old.