When the world's most endangered whales migrate to the Florida coast each winter, researchers fly over the ocean and scan from the shoreline to find them.This year, they not only can see the right whales, but can hear them too.An acoustic buoy has been set up off the Jacksonville coast, broadcasting the call of the right whales 24/7 since December.Whale calls were heard well before research teams spotted the creatures regularly, offering yet another means to track them, said Barb Zoodsma, a biologist with the National Oceanic and Atmospheric Administration."We can get the acoustic hits even before we had visual detection," said Zoodsma, coordinator of the right whale recovery program in the Southeast. "It's good information that verifies what we know — that right whales are in the area."The North Atlantic right whales head to the coast of southern Georgia and northern Florida in the winter to birth their calves. Nearly hunted to extinction in the 1800s, right whales today number less than 400. They remain at risk because of deaths from ship strikes and fishing-line entanglement.Their annual migration triggers a major effort to track them, with research teams surveying the ocean from Savannah, Ga., to St. Augustine to find them. Along the Flagler, Volusia and Brevard coasts, volunteer teams also watch for the whales, which are known to swim close to shore.Last year, the teams spotted 39 right whale calves, a record for the number of calves seen in a season. This winter, there have been at least seven calves with their mothers and another 40 whales that have also returned to the vicinity.Each whale sighting offers vital information that is sent to the surrounding vessels to avoid collisions. But bad weather often grounds the flight crews.>From the buoy bobbing off Jacksonville, and another buoy off Savannah, the scientists can still confirm a whale is within a few miles, said Christopher Clark, who heads the bioacoustic research program at Cornell University.The buoys, anchored in 45-foot-deep water, can routinely detect sounds up to five miles around, though the noise of passing vessels makes it hard to hear. The project receives federal funding from NOAA.Similar buoys are already stationed off the coast of Cape Cod, Mass., where the right whales feed during the summer. The buoys are lined up along a 55-mile stretch of the main shipping channel so as to provide regular audio warnings about the whales.Right whales make an array of different vocalizations but the "up-call" is a two-second that sounds like a deep, rising "whoop."It's not the melodious, lengthy whale songs that humpback whales vocalize during the mating season, but Clark said, "It's their basic call that helps to keep the herd coherent."A computer on the detection buoy filters out the up-calls against shipping noise and other sounds and broadcasts the sounds via satellite to the Cornell lab. Once the sound is confirmed to be a right whale call, that information is sent to the right whale research teams and to mariners.More buoys can help the conservation efforts, Zoodsma said. The audio hits would be particularly helpful in November and in the spring, when there aren't survey flights, and in areas that aren't covered by the surveys.What the call means, and which whale said it, is unknown. "Whales of all ages can make this kind of sound and I'm convinced that they can tell each other apart," Clark said. "It would be fantastic if we could make out whether the call is by a male or female, young, old or a calf."