Birds and the Bees

I've been looking for the explanation of the Idiomatic expression: "the birds and the bees" which means sex.

I found a posting under UsingEnglish:

1 : Birds and the bees
If a child is taught about the birds and the bees, they are taught about sex.

However, I still don't understand what's the connection of the birds and the bees to sex. Can you please explain this to me?

Thanks.

Virgil

[Anglika]

It is one of those idioms which has been around for a long time and has no specific origin. This link has a reasonable discussion of it> World Wide Words: Birds and the bees