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What: Breeding tropical seabirds, neotropical migrants, and the possibility of rare strays. The Dry Tortugas provide the only regular nesting site for Sooty Terns, Masked Boobies, Brown Noddies, and Magnificent Frigatebirds in the continental U.S.

Where: The seven coral islands that make up Florida’s Dry Tortugas National Park, 70 miles west of Key West.

When: Spring migration: early April to mid-May; fall migration: July to November.

Throughout their history, the Dry Tortugas have been home to everything from Spanish colonists and shipwrecks to Civil War prisoners and yellow fever. Their most enduring legacy, however, lies in the sheer amount of biodiversity that is packed into the little island chain. 

Dry Tortugas National Park encompasses 100 square miles of mostly open water, save for seven small coral keys that have been known to host, the vast majority of which are migrants or strays. In spring, migrating neotropical seabirds begin arriving from Mexico, Central, and South America as early as January, with migration climaxing in droves of northbound songbirds from April to mid-May. Fall migration, which lasts from is more subdued but still a spectacle in its own right, bringing a variety of raptors, including Peregrine Falcons, Merlins, and Sharp-shinned and Broad-shouldered Hawks heading south. 

For birders, spring migration is the main attraction in the Tortugas, offering an alluring mix of breeding rarities and exhausted migrants after traveling nonstop over the Gulf of Mexico. During peak migration, this can lead to visitors seeing a mind-boggling variety of birds, including prized species like Hooded Warblers, Yellow-throated Vireos, and Summer Tanagers. in early spring can lead to even larger and diverse flocks of migratory fallouts. “They drop out any time they find a brief respite,” says Julie Wraithmell, the executive director for . “And the Dry Tortugas have a giant rest stop sign on it.” In addition to these migrants, Caribbean specialties are also on the menu, including the White-tailed Tropicbird, Antillean Nighthawk, and Black Noddy—possibly the top target species for birders visiting the Tortugas. 

Of the seven keys, only Garden and Loggerhead Keys are regularly accessible to the public, but the former has one of the best birdwatching sites in the country: Fort Jefferson, an American military base dating back to the mid-1800s. Once a formidable military presence in the Straits of Florida, the site now houses the sole source of freshwater for migrating birds via a fountain maintained by the National Park Service (NPS). Hoping to find Golden-winged Warblers, Black-whiskered Vireos, and Rose-breasted Grosbeaks all in one spot? Just grab a seat on one of the benches surrounding the fountain, according to Mark Hedden, the executive director for the Florida Keys ���Ϲ��� Society. Tired and parched, most birds vying for a spot are unconcerned with human onlookers. “They will come in and just hit that fountain over and over again,” Hedden says.

Visitors able to climb the three stories to the top of the fort will be rewarded with another treat: Close glimpses of the Magnificent Frigatebirds that hover above the island. Home to about , nearby Long Key is the of the angular seabird in the United States. Sporting an impressive, inflatable throat sac and a 7-foot wingspan, Magnificent Frigatebirds are among the largest and flashiest birds the Dry Tortugas has to offer. “You can probably get as close as you'll ever get to a Magnificent Frigatebird if you sit up on top of the fort,” Hedden says. “I've lived in the Florida Keys for 30 years, and I still stop every time I see a frigatebird. They're just such amazing things to look at.”

Along with those soaring frigatebirds, birders can rely on seeing some of the Tortugas’ other residents wheeling about in the sky. Roughly  and more than  (and the occasional Black Noddy) return each year to breed and nest on Bush Key, the only regular nesting site for both species in the continental U.S. The Sooty Terns begin making landfall in January, but they can be heard approaching the island on late December nights thanks to their cacophonous calls, says Glenn Simpson, park manager for Dry Tortugas National Park. Once the breeding season ramps up in March, Sooty Terns dominate Bush Key until August. The Brown Noddies, which usually arrive with the Sooties, continue to occupy the key until October. The NPS closes Bush Key to the public from February to September to accommodate the nesting birds, but not to fret: Equipped with a good scope, you can park yourself atop Fort Jefferson and spy on their raucous colonies, which can be heard day and night. “It’s a great thing—the Sooty Terns and the Noddy terns, they make a lot of noise.” Simpson says. “It's just a part of life at the Dry Tortugas, and you get used to it.” 

The Dry Tortugas have been noted for their rich biodiversity since Juan Ponce de Leó��&�Բ�����;first documented them in 1513, with the likes of and geologist conducting surveys of the keys in the 1800s. The Dry Tortugas that ���Ϲ��� and Agassiz witnessed weren’t the same collection of islands visitors visit today, though. In 1832, ���Ϲ��� described the famous Sooties and Noddies of Dry Tortugas nesting on an island called “Bird Key.” A century later, Bird Key, forcing the terns to seek refuge on other islands. Since the keys are mostly sandy deposits, they’re regularly reshaped by erosion and severe weather. According to Simpson, aerial images show that Loggerhead Key has been steadily shifting southeast over the past decade. “The northwestern shoreline is eroding significantly each year, and it's building on the opposite shoreline,” he says. “So the island is in motion.”

Know Before You Go: Visitors can only access the Dry Tortugas by private boat, commercial seaplane, or aboard the , a 175-passenger commercial ferry that departs daily from Key West. Those opting to arrive by seaplane or ferry should reserve early, since spots can sell out months in advance. With the ferry and seaplane only bringing visitors to , arranging a private boat can offer more access. According to Simpson, Hospital Key (named after a hospital for Fort Jefferson inmates built in the 1870s) and Loggerhead Key (home to a year-round population of 40 or so Masked Boobies) can be approached by boat or kayak. While Hospital Key is closed to the public, Loggerhead is open to visitors during daytime hours. But from the water, you can still get close enough to Hospital Key to take photos of the boobies, says Simpson. 

While all birders should pack binoculars and, ideally, a scope for birding at Dry Tortugas, those aboard the Yankee Freedom or private boats also have a chance to see a wider assortment of pelagic seabirds on their way to the park. The sun can be brutal on the open water, though, so don't forget your hat and sunscreen. Simpson advises visitors to wear reef-safe sunscreen to help out the park’s corals, which have suffered from an infectious disease known as Stony Coral Tissue Loss Disease.

Guests can also choose between taking a day trip or camping trips of up to 4 days. Parties of 10 campers or more will need to apply for a through NPS. Smaller groups are able to claim a campsite on a first come, first served basis and can pay for after arriving on Garden Key. For Wraithmell, camping gives visitors a chance to explore other opportunities the Dry Tortugas offer outside of birding. “You'd be remiss if you didn't enjoy the dark sky while you're camping there,” Wraithmell says, “and experiencing the Milky Way away from the lights of the city.”