All crows under heaven are equally black. (Bad people are the same everywhere.)
Tips
culture
In Chinese culture, crows are traditionally seen as unlucky birds. The proverb 天下乌鸦一般黑 (all crows are black) means corrupt people are the same everywhere. However, in some ancient texts, crows symbolized filial piety because they were believed to feed their aging parents.
memory
乌 means 'black/dark' and 鸦 means 'crow' - so 乌鸦 literally means 'black crow', which is fitting since they are entirely black.
