Migration of birds is a fascinating story. Many birds across the world travel to different locations in search of food and a warm place to breed. A new study has now found a dark side of the fascinating tale of migration -- the risk of spread of diseases. The researchers have studied two species of migratory birds and have identified the presence of two strains of parasites in them that could potentially spread the disease to the local bird population, which do not have the required immunity to fight against them. The researchers warn that their finding could put the entire local bird population at the risk of contracting the diseases.