He glimpsed it for a few seconds, but Nico Sarbanes knew instantly the large brown seabird was an unusual visitor to the Baltimore harbor when he spotted it on a visit to Fort McHenry with his family, including his father, U.S. Rep. John Sarbanes.
The 21-year-old remembered the bird's distinctive white breast, chocolate brown body and long, conical beak from studying the markings before an unsuccessful search for the rare bird, reported on Assateague Island in 2009.
Could it be a brown booby?
Few local birding enthusiasts took Sarbanes' report to a local birdwatching email list seriously. In North America, the seabirds usually are found nesting near the Dry Tortugas, a small group of islands west of the Florida Keys.
But nearly two weeks later, water taxi captain Deborah Rowan, herself an experienced birder and former crewmate of the Pride of Baltimore and Lady Maryland, spotted the birds and knew distinctive markings and diving patterns were special.
"When an unusual bird comes along, it is very noticeable," she wrote in an email alerting the Audubon Naturalist Society, which promptly shared the message with the local birding community.
Over the past week, the spectacle has lured an estimated 150 or more birders to the harbor, a chance to add a new and rare species to lifetime sighting lists. It likely will become only the second confirmed brown booby sighting in Maryland.
"It's become a huge cause celebre for the Maryland birding community," said Mark Hoffman, acting deputy secretary of the Maryland Department of Natural Resources and the leader on the Maryland Ornithological Society's "Maryland Life List." The brown booby is the 417th species he has spotted in the state.
At least two brown boobies have spent the month perched on a thick rope slung between two former Navy cargo ships — the Denebola and the Antares — that are part of the U.S. Maritime Administration's Ready Reserve Fleet and docked at the North Locust Point Marine Terminal.
The agency is used to wildlife encounters, and the boobies' presence is not affecting vessel operations, spokeswoman Kim Strong said.
"We encourage local birdwatchers to enjoy viewing this rare sighting while maintaining a safe distance from the vessels," she said in an e-mail.
To see them up close, bird watchers have flocked to water taxis — and to kayaks and even a kind stranger's boat. But the boobies also have been spotted from Tide Point to the northwest and Fort McHenry to the southeast.
While steering the Harbor Connector Sept. 16, Rowan watched the birds dive for lunch along the Canton waterfront, near Captain James Crabhouse. Their dive is unique, birdwatchers say — they hover lower over the water than their relatives, such as gannets, before speeding into the water headfirst.
"Nothing else I've ever seen in the harbor dives like that," Rowan said.
One of the boobies is an adult, with its characteristic sharp delineation between the brown feathers covering its head, neck and body and the white along its belly and underneath its wings. The other is a juvenile, its underside a muddy tan rather than the clean white of its elder. They are living among a colony of native cormorants.
Brown boobies are indeed out of place in the Chesapeake, said Jack Cover, general curator of the National Aquarium.
They typically stick to more tropical waters, but have been known to travel up the coast, perhaps heading toward land if they aren't finding fish near the surface in the open ocean, he said. It's a transitional time of year for small bay fish like menhaden, which are leaving shallower tributaries for deeper waters. An abundant food source is likely keeping the boobies in Baltimore, for now.
There have been reports of boobies from unusual places around the country over the past month — from Provincetown, Mass., at the tip of Cape Cod, to reservoirs on the Virginia/North Carolina border, some 150 miles from the coast, and even in Iowa.
There is only one record of a brown booby sighting in Maryland, said Phil Davis, secretary of the Maryland Ornithological Society's Maryland/District of Columbia Records Committee. A park ranger photographed it sitting on an Assateague beach in August 2009.
There is a high bar for such a rare bird sighting to be made official. If a birdwatcher's description is too vague and the committee cannot rule out another bird species, it won't accept it. For example, a brown booby was reported in the Chesapeake near Stevensville in September 2011, but the committee could not be sure it wasn't a more mundane species based on the description, Davis said.
The committee won't review the Baltimore booby sightings until the birds head south for the winter, and it can take four months or more for the panel to decide, he said. (Birdwatchers' many photos of the birds "are very clear and seem definitive," he added, being careful not to predict how the committee might rule.)
But for the dozens of birdwatchers thrilled by a chance to add such an exotic species to their life lists, there is no need to wait.
"For me, I'm marking it down as a yes," said Denise Ryan, who lives in the Washington, D.C., area and drove to Baltimore to catch a glimpse Sunday. "I saw two brown boobies and I'm checking it off on my life bird list."
The opportunity likely won't last much longer. The weather will soon turn colder than the birds prefer, sending them southward along with many other migratory birds.
Bird lovers and environmentalists said the visit is nonetheless a reassuring sign in efforts to restore natural habitats in the Chesapeake. Cover said aquarium officials have recently been pleasantly surprised by an abundance of turtles, crabs and ospreys around Masonville Cove, where a former scrapyard was turned into a wildlife conservation area in recent years.
"That's probably happened for eons, that [brown boobies] have come up the coast and come to the Chesapeake Bay," Rowan said. "They're still doing it, so you can't give up on it."