The black billed swan, also known as the trumpet swan, is the largest native waterfowl in North America and is named after its unique horn like call. The body length is usually between 138 and 165 centimeters, the wingspan can reach 185 to 304.8 centimeters, and the weight is between 7 and 13.6 kilograms. They are the heaviest flying birds in North America. Due to overfishing and habitat loss, the population sharply declined in the early 20th century. By implementing protective measures and reintroducing the project, the population has now recovered to some extent

It is a widely distributed waterfowl of the duck family. Known for its bright green head in males and simple brown feathers in females. Medium in size, males are usually more prominent than females, with a distinct green crown and white neck ring, while females have a brown body with mottled patterns. It is an omnivorous animal that mainly feeds on aquatic plants, insects, small fish, and small aquatic animals. It breeds in many wetlands, lakes, and rivers in the northern hemisphere, especially in Europe and Asia. It is a migratory bird that flies from its breeding grounds to its wintering grounds every autumn. The migration route covers a vast area, sometimes even crossing continents.

It is a waterfowl famous for its green feathers and metallic luster on the male's head. The male bird has a white collar around its neck and metal purple blue wing mirrors on its wings. Mainly inhabiting water areas rich in aquatic plants, omnivorous animals that feed on plants and small animals. They are migratory birds, migrating in spring from March to April and in autumn from September to November. They have unique sleeping habits and can turn one eye open or closed during sleep, which helps them stay alert in dangerous environments. In addition, the mallard is the ancestor of Chinese domestic ducks and has important economic and medicinal value. The mallard is also a protected species.