Brown willow warbler (scientific name: phylloscopus fuscatus) is a small bird with a body length of 11 to 12 cm. The upper body is brown or olive brown, the inner coverts of the wings are the same color, the rest of the coverts and flight feathers are dark brown, the outer feather margins are light brown and slightly olive-embellished, and the inner feather margins are light grayish brown. The tail is dark brown , some of which are slightly stained with a pale brown , and the plumage is paler with a distinct olive brown. The brow stripes are brownish-white from the base of the forehead to the occipital, the dark brown of the eye stripes extends from the eye through the eye to the occipital side, and the cheeks and ear cover feathers are brown and mixed with light brown. The chin and throat are white with a slightly stained skin yellow, the thorax is light brown, the abdomen is slightly stained yellow or gray, the two sides are brown, the tail coverts are light brown and sometimes slightly brown, and the axillary feathers and underwing coverts are also skin yellow. The old summer feather upperparts are a little gray. Juveniles are similar to adult birds , but have darker upperparts , pale greyish-white eyebrow lines , and pale brownish-yellow undertones. The iris is dark brown or black brown, the upper mouth is dark brown, the lower mouth is orange-yellow, the tip is dark brown, and the feet are light brown.
China is distributed in the northeast of Inner Mongolia, Daxing'anling in the north of Heilongjiang Province, Xiaoxing'anling in the northeast, Yichun, Mudanjiang and Harbin in the south, Changbaishan in the east of Jilin Province, Yanbian, Tonghua in the south, Hunjiang in the south, Siping in the southwest, Liaoyuan, Baicheng in the west, Dalian, Jinxian, Yingkou, Liaoyang in the south of Liaoning, Chaoyang, Jinzhou, Yixian in the west, Beijing and Henan, Sichuan, Gansu, Ningxia, Qinghai and Inner Mongolia Yikezhao League in the east (breeding birds); Shanxi, Shaanxi, Hubei, Hunan, Sichuan, Guizhou, Yunnan, Tibet, Guangxi, Guangdong, Hong Kong, Fujian and Hainan Island, occasionally found in Taiwan.
It inhabits montane forests from the foothill plains to the alpine shrublands above 4500 m above sea level, and prefers sparse and open broad-leaved forests, mixed coniferous and broad-leaved forests and coniferous forest margins, as well as sparse forests and shrublands along streams, and dislikes dense forests. During the non-breeding period, it is also found in farmland, orchards and small jungles near houses. It is often active alone or in pairs, mostly in understory, forest edge and streamside shrubs and grasses. He likes to jump between branches, or jump up and down, constantly making sounds similar to "rattle, rattle-", or "answer, answer, answer-". During the breeding period, it often stands on the branches of the shrub and sings non-stop from morning to night, and its sound is like "bullying, cheating, cheating, cheating-" A continuous call that is constantly repeated. Sometimes standing on the branches and singing, sometimes flapping their wings and soaring in the air, sometimes flying from one branch to another, and in case of interference, they immediately fall into the bushes. Diet: Feeds mainly on insects. According to the 8 bird stomachs dissected in Changbai Mountain, the food eaten by Coleoptera insects is the majority. Migration: The brown willow warbler is partly a summer migratory bird in China, and some is a winter migratory bird and a traveling bird. Most of the breeding grounds begin to move in early May, autumn begins to move away in late September and early October, and at the latest in Changbai Mountain at the end of October.
The breeding season is from May to July. Nests usually nest in understory or in bushes along the edge of forests and streams, and the nests are 0.27 to 0.7 m above the ground, and there are also reports of nesting directly on the ground in the bushes. The nest is spherical in shape, with the opening of the nest opening near the apex on the side. According to the size of the nests measured in Changbai Mountain, the two nests are: the outer diameter is 12 to 15 cm, the inner diameter is 6 to 6 cm, the height is 13 to 14 cm, and the nest mouth is round and the diameter is 4 cm. 4 to 6 eggs are laid per clutch, usually 5, the eggs are white,