( CNN ) -- Flying penguins are unusual . Especially when they fly on a C-130 Hercules military plane . Almost 400 lost Magellanic penguins march back to the sea after being rescued by animal-welfare groups . In Brazil , 373 young Magellanic penguins were rescued , rehabilitated and released last weekend after their search for food left them stranded , hundreds of miles from their usual feeding grounds . Animal-welfare activists loaded the birds onto a Brazilian air force cargo plane and flew them 1,550 miles to the country 's southern coast , where a crowd of onlookers celebrated as the penguins marched back into the sea . `` We are overjoyed to see these penguins waddle back to the ocean and have a second chance at life , '' said veterinarian Dr. Valeria Ruoppolo of the International Fund for Animal Welfare , the group that oversaw the rescue . See photo gallery of rescued penguins » . Magellanic penguins are warm-weather birds that breed in large colonies in southern Argentina and Chile . The young animals then migrate north between March and September , following their favorite fish , the anchovy . The birds are named after Portuguese explorer Ferdinand Magellan , who first saw them in 1519 . But changes in currents and water temperature apparently confused the juvenile birds , who strayed too far north to the warm beaches of Salvador , Brazil , 870 miles north of Sao Paulo , Brazil . Watch the penguins march into the sea » . Starting in mid-July , in the northeastern Brazilian state of Bahía , `` It was just about raining penguins , '' Ruoppolo said . `` There was not much of a food supply . The birds were stranded and emaciated . They had lost all their muscles and body condition . '' While occasionally a few birds show up so far north , the unusual sight of hundreds of wayward penguins posed a challenge for animal conservation groups . `` We had to learn how to work with them , '' said Carlos Garcia , a spokesman for IBAMA , the Brazilian Institute for Environment and Renewable Resources . `` Fewer than 20 penguins usually wash ashore , but with such a large number , we had to really understand their biology and learn how to treat them . '' The Instituto Mamíferos Aquáticos ( Institute for Aquatic Mammals ) also fed and cared for the hungry and disoriented birds . Ruoppolo , who is also the emergency relief officer for IFAW , has a lot of experience saving penguins and other animals injured in oil spills . Last week she worked with conservation groups and volunteers to save as many of the birds as possible . `` We showed them how to stabilize the animals , to feed them and give them proper care , '' she said . Healthy Magellanic penguins grow to about 27 inches tall and weigh about 9 pounds . Ruoppolo said IBAMA -- the government 's environmental authority -- and the Brazilian military were supportive throughout the unusual relocation mission . On Friday , the penguins were loaded into special crates and put onto the plane for the journey to Pelotas , in southern Brazil . After their first-ever flight , the birds went on a truck ride to the Center for Recovery of Marine Animals , where they rested for 24 hours . The birds released at Cassino Beach the next day had to meet very specific health criteria , said Ruoppolo . `` Their feathers had to be waterproof , their overall body condition had to be good , their lungs healthy , and they had to be able to catch food , '' she said . The youngsters had some adult supervision for their return to the wild . They were released with a small group of adult penguins that had been nursed back to health after surviving an oil spill . Scientists expect the older birds will help guide the little ones to nearby feeding grounds . Some penguins are still being cared for , both in the north and south of Brazil . The newly released birds have bands on their flippers so scientists can follow their progress and learn more about their migratory habits . Of more than 1,600 penguins that washed ashore in northern Brazil , about half are still alive . That is a fairly good outcome , given the fragile status of young birds on their first migration , said Ruoppolo . `` For all species you have animals that die within the first year , '' she said . And without quick human intervention , the consequences would have been much worse . At this point there is no way to know exactly why the animals became stranded . While the Magellanic penguin population is not in jeopardy because of this one event , Ruoppolo said there are other threats , primarily from overfishing . CNN 's Paulo Nogueira contributed to this report .
Activists rescue group of young penguins who migrated too far north on Brazil coast . Penguins loaded onto a C-130 Hercules military plane and flown south . To cheers of onlookers , penguins return to ocean near their feeding grounds . Changing currents , temperatures may have led the confused birds off course .