Recently, bird watchers Philip Hyde and Paul Hyde found an American green-winged duck (Anascaro linensis) in Shanghai's Nanhui Dongtan, a new record for Birds in Shanghai.
The green-winged duck (scientific name: Anas crecca) is a small duck with a body length of 37 cm and a weight of about 0.5 kg.
Green-winged ducks used to be quite abundant in China, not only widely distributed, but also extremely large in number, migrating thousands of them, one after another, like a cloud in the sky, all over the waters of southern China, is China's largest number and most common industrial hunting birds. But it's hard to see such a spectacular scene, with a significantly reduced population.
The American Green-winged Duck is similar in size to the native Anas crecca, but differs in the distribution of color patches of feathers, with the Yellow outer edge of the Face Green-Eyecup skin of the American Green-winged Duck's head not as pronounced as the native, and a vertical white stripe at the shoulders, while the native Green-winged Duck's tertiary flight feathers have transverse white markings. The American green-winged duck mainly lives in North America and rarely appears in China.
Today, the American green-winged duck is in Shanghai for the first time, and my first thought is not the beautiful green-winged duck, but the water hyacinth, an invasive plant that has caused great economic losses to China before.
Water hyacinth, native to South America, originated in Brazil, due to the control of biological predators, only an ornamental population scattered in water bodies, in 1844 at the American Exposition was described as "beautifying the world's lilac corolla". Since then, water hyacinth has been introduced as an ornamental plant, which is an unexpected thing, this ornamental plant, after leaving Brazil, but in Asia, Africa, Europe, North America and dozens of other countries caused harm, a large number of reproduction. After its gradual introduction to China, it was promoted and cultivated as an ornamental and water-purifying plant, but escaped into the wild. Due to its extremely fast asexual reproduction rate, it has been widely distributed in 19 provinces and cities in North China, East China, Central China, South China and Southwest China, especially in Yunnan (Kunming), Jiangsu, Zhejiang, Fujian, Sichuan, Hunan, Hubei, Henan and other provinces, and has spread to temperate areas, such as Jinzhou and Yingkou. Due to rapid reproduction and almost no competitors and natural enemies (although there are many wild, domestic animals that feed on their stems and leaves, but the amount of food is small, compared with its huge growth rate), it has developed rapidly in the rivers and lakes in southern China and has become one of the main invasive alien species in China's freshwater water bodies.
The arrival of the American green-winged duck is a surprise that will make our Chinese lake more colorful, not more of a scourge.