Migrating birds of prey draw visitors to the Florida Keys

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 humid, shirt-soaking 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 sky for migrating raptors — birds of prey, a group that includes falcons, hawks, ospreys, eagles, and kites — as they passed on their months-long journey to the Caribbean or 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 last 12 years, Curry Hammock State Park on Little Crawl Key has hosted this Hawkwatch, one of more than 100 fall surveys 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 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 birds into a concentrated stream. Curry Hammock in the fall is one of the few places in the world where birders can expect to see migrating peregrines. “I guarantee it,” Gles said.

His confidence is not misplaced. Counters here logged 1,506 peregrines on Oct. 10, 2015, the highest daily count ever recorded anywhere in the world. This season during the count, 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.

"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."

“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 slightly to the right.

"Looks like another peregrine. Adult.”

Spotters counted only 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, 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 records the number and kind of raptors seen in the previous hour. At the end of the day, daily totals for each species are uploaded to Hawkcount.org. Non-raptor counts are uploaded to Ebird.org, maintained by the Cornell University Lab of Ornithology.

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 birders’ eyesight and identification skills. To meet the challenge, spotters spoke in a cryptic code passed down from one team of hawk-watchers 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 was 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 tip-off. “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.”

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,” said Jeff Payne, Chris’ father.

An 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 the previous day’s count and entered this day’s: 47 peregrine falcons, 37 ospreys, 25 merlins, 11 broad-winged hawks, six northern harriers, and a handful of other raptors — 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. "Personally, the variety of raptor species and number of peregrine falcons are what sets [the Keys] above other hawkwatches for me."

Curry Hammock State Park: 305-289-2690 or floridastateparks.org and search for Curry Hammock.

Additional information: keysaudubon.org or floridakeyshawkwatch.com