Forest officials have sounded a bird flu alert at the habitats of migratory birds' in Bhitarkanika National Park here following detection of flu infection in Karnataka. Precautionary measures have been initiated to find out possible flu infection of avian species here, forest officials said. "A joint field survey by wildlife personnel and state veterinary wing officials is currently under way within the bird-infested pockets of the national park," said Forest Range Officer (FRO) A K Nayak.