The Eurasian tree sparrow (Passer montanus) is a charming passerine bird, easily recognized by its rich chestnut crown and nape, and a distinctive black patch on each pure white cheek. Both sexes are similarly adorned, and the juveniles mirror the adults, albeit with slightly duller hues. This species is somewhat smaller than the closely related house sparrow, and its size is approximately 12.5–14 cm in length, with a wingspan of about 21 cm.
To identify the Eurasian tree sparrow, look for the kidney-shaped black ear patch on each white cheek, the black chin and throat, and the light brown upperparts streaked with black. The wings bear two narrow white bars, and the legs are pale brown. The bill is lead-blue in summer, darkening almost to black in winter. Unlike the house sparrow, there is no sexual dimorphism in plumage, making both males and females equally easy to identify.
In Europe, the Eurasian tree sparrow is typically found in lightly wooded open countryside, while in eastern Asia, it is more common in urban settings. It prefers nesting in natural cavities, holes in buildings, or even the abandoned nests of other large birds. This species is not typically found in mountainous regions, despite its scientific name suggesting otherwise.
The Eurasian tree sparrow has a broad distribution across temperate Eurasia and Southeast Asia, and it has been introduced to other regions such as the United States. Its range extends from Europe across Asia to the Lena River and south to the northern regions of Turkey, the Caucasus, Kazakhstan, Mongolia, and North Korea.