 What a nice view, the sky covered by thousands of birds! Twice a year, billions of birds migrate as seasons change, seeking overwintering areas or safe nesting areas with sufficient feed for their young ones. Unfortunately, some of these birds may carry pathogens that can harm people and animals as they move across geographic borders. One of the dangerous diseases of recent years, avian influenza, is associated with migratory birds. Outbreaks of avian influenza have led to the death or culling of millions of poultry and pigs and untold millions of dollars in losses to farmers and producers. Avian influenza is also a deadly disease that affects humans. Since its inception in 1964, the Joint FAO IAEA Division is working with rural communities and veterinary services around the world, applying nuclear and related techniques to reduce the risk of diseases in farm animals, including those of risk to humans. A specific focus is on technologies that allow the identification of a pathogen before the outbreak of the disease. In the case of avian influenza, a stable isotope composition of a bird's feathers, claws or beaks reveals where the migrating bird began its journey. Molecular techniques can detect the presence of viruses, such as avian influenza in droppings of infected birds, and can pinpoint the species of birds that are infected. Combining the information gathered by these techniques, researchers can track those birds as they travel, determine where they come from, what paths they have taken and which species are carrying the virus. This gives veterinary services a head start in predicting sites at higher risk of outbreaks. Nuclear and nuclear related techniques are highly accurate, sensitive and non-invasive. Their use offers tremendous advantages for disease monitoring in wild birds and can contribute effectively to reducing the risk of diseases spreading.