From discussion on useless-faq, like pigeons, or more precisely, pigeon pairs recognize each other.

Aaa: I have the same question about the Chinese: how does the Chinese jinn know in the evening that it is her husband who came home, and not a neighbor?
BBB: She puts the mark on the cross.
ccc: The problem is that they all have crosses. And the number of possible flowers is much less than the number of husbands.
ddd: Each cross has its own shape. In fact, there were hieroglyphs.