A delicately feathered roseate spoonbill, a whopping 461/2-pound barracuda, a Florida manatee, and a host of other exotic visitors vacationed on the Jersey Shore this summer.

This isn't the lead-in to a stand-up routine. It's the result of an odd ecological convergence that has attracted species from as far away as the Florida Keys for extended stays on the New Jersey coast.

Were they lured by the tropical water temperature, which stayed around 80 degrees for more than a month and extended all the way to the ocean canyons, some 70 miles offshore? Did the unexpectedly high tides in June and July carry them here? Was it the wet spring? Global warming?

Biologists and ocean scientists can't say precisely what has prompted species more common to warmer climes to extend their ranges, but this summer has been a treat for birders, fishermen, and naturalists.

Mother Nature choreographs the rituals of migration and mating each spring and summer. Fish, such as menhaden and herring, that serve as food for larger species travel north, drawing game species like tuna and grouper behind them.

Shore birds including egrets, ibis, and herons also come from southern waters, pulling crayfish, minnows, and other nutrition from the ocean and marshlands. Some mate or lay eggs; others seek only the bounty they find on the way.

But sometimes species that don't normally migrate meander into the region, perhaps to expand their range after familiar habitats shrink, biologists say.

"Nature does sometimes provide a wonderful opportunity for people to be able to see things in an area where they normally wouldn't," said Bob Schoelkopf, founder of the Marine Mammal Stranding Center in Brigantine, N.J. "Each summer is a different array."

Take the manatee that has hung around the Raritan River and Raritan Bay north of Sandy Hook all summer. Schoelkopf has been keeping an eye on the tropical mammal, and the U.S. Fish and Wildlife Service is tracking it to see whether it's the one that has been spotted as far north as Cape Cod in recent years.

Pelicans, a rare sight in New Jersey two decades ago, now are regulars in these parts. Biologists theorize that the large, stocky birds - whose range had been south of North Carolina, in South America, and on the Pacific Coast - may soon nest here, Schoelkopf said.

Though it's usual for the unusual to show up on the New Jersey coast every now and then (the state's situation on a key north-south migration route usually results in a couple of "Wrong-Way Corrigans" each year), it is rare that so many southern species appear in one season, say some.

"I've never seen so many different things from southern waters coming in during one summer, and so big when they do come in," said Dennis McVay, a fisherman who sells bait and weighs catches at Jim's Bait & Tackle in Cape May.

McVay was shocked this month when a Pennsylvania man brought in a 461/2-pound barracuda he said he had caught off Cape May.

"It was a monster, for what it was. It stopped traffic," said McVay, who added that the fish had been weighed outside on his shop's scale.

A 20.8-pound barracuda set a local fishing-contest record in 1998, said Mike Shepherd, 65, of Linwood, N.J., a longtime outdoorsman and a retired Jersey Shore sports editor. No state record is kept for the species because it is so rare here.

Although 80-degree ocean water isn't rare, it is unusual for such a big area to remain warm for so long, Shepherd said. That may have contributed to the presence of so many unusual fish, such as cobia, trigger fish, wahoo, and particularly large white marlin.

Another anomaly was higher-than-expected East Coast tides in June and July. The National Oceanic and Atmospheric Administration makes its tide charts months in advance, but around mid-June, NOAA scientists noticed that tides from Maine to Florida were between six inches and two feet above predicted levels.

This week, the agency will announce in a 30-page document that it attributes the temporary rise to a persistent, widespread southwest "wind field" over the Atlantic Coast and a subtle weakening in the Florida Current.

The current feeds into the Gulf Stream and can influence water depth for thousands of miles. The large wind field helped push more water than usual onto the entire Atlantic coastline, said Mike Szabados, director of NOAA's tide and currents program.

The agency will keep studying why the current weakened temporarily and how it influenced the tide. The data may help determine whether the tides influenced the migration of typically southern species, Szabados said.

Vince Alia, a research associate for the New Jersey Audubon Society's Cape May Bird Observatory, said he was interested to see whether the findings could account for some birds that visited New Jersey this summer.

"This area has long been considered what we would call a 'vagrant trap' for various bird species," Alia said. New Jersey's southern shoreline and cape act as a kind of funnel for migrating birds of all types.

But every now and then a truly atypical species shows up, like the roseate spoonbill spotted in the Edwin B. Forsythe National Wildlife Refuge, in Galloway Township, inland from Brigantine and Atlantic City, he said.

The roseate spoonbill is a stunning, long-necked creature with feathers a deeper pink than a flamingo's and a spoon-shaped bill that helps it scoop food from the wetlands depths. No one can say for sure why it was there, Alia said.

"That's what makes birding and watching other nature so exciting," he said. "We can never really know why or how something ended up in a particular place for 30 seconds or for weeks and even months."

Contact staff writer Jacqueline
L. Urgo at 609-823-9629 or jurgo@phillynews.com.