Birds of a feather flock together is a popular English proverb used to describe how people with similar tastes tend to seek out each others company. In Chinese there is a similar expression, 物以类聚, which literally means like attracts like.

The Chinese phrase is more than 2,000 years old. The phrase is said to have originated during the Warring States period (475-221 BC). A renown scholar, Chun Yukun, was asked by King Xuan of the State of Qi to bring other talented people like Chun to the King's court. For Chun, fulfilling this request was literally a walk in the park. As a respected scholar himself, Chun spent alot of his time mixing with other respected scholars, so he knew exactly wher to find them - as he said to the King:

Birds of the same type often fly together and animals of the same type are often seen walking in groups.

This tendency of people to gravitate toward those who are similar still rings true today and, arguably, is a big reason why large communities naturally divide into groups.

Some argue that the Chinese idiom, 方以类聚, is also an equivalent expression.