From July to September 2011, when both groups respectively conducted bird monitoring investigations, they discovered a rare endangered bird species—Egretta eulophotes—that ranks high on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species in the lagoon of Dongsha Island. According to past investigative reports, Egretta eulophotes appear in the lagoon area of Dongsha Island ever year from April through September. They are migratory birds and usually live in the same habitats with other heron species. These birds rarely appear as one and are extremely precious.

Egretta eulophotes are also called Yellow-bill Egrets. Originally, the large population of these birds was spread out across the Southeast Asia region, including Korea, along the eastern coast of China, Taiwan, Philippines and Sydney, Indonesia. At the beginning of the 20th century, due to the high demand of the plumage trade, large amounts of Yellow-bill Egrets were slaughtered and the population dwindled drastically. Currently, only small islands along the sea of China, North and South Korea, and Russia have breeding records of the birds.

The lagoon of Dongsha Island provides an excellent resting and feeding environment for birds that are passing through or making it through the winter.  It is an important relay station for migratory birds migrating from the south to the north.