World Migratory Bird Day The theme for this World Migratory Bird Day is Sing, Fly, Soar – Like a bird! At the UNESCO World Heritage Centre, we support natural sites around the world in their conservation efforts, which in turn supports animals in maintaining their natural behaviors in healthy habitats. Bird song is not only enjoyable to listen to, but scientists and site managers can use it to evaluate the health of a forest. In 2020, a study was published by the Area de Conservación Guanacaste (Costa Rica), where bioacoustics were used as an indicator for biodiversity. The results show that the older the forest, the noisier it is, due to an increased number of birds. Older and healthier forests are more diverse, and better environments for the species they support.