Last night, I was talking about sex with some guys . . . wait, that doesn’t sound right. I was talking . . . I was minding my own business when suddenly someone asked me what ‘the birds and the bees” had to do with . . . the subject at hand.
Today I have an answer from our Etymology Desk: We don’t know. The phrases appears to have developed last century, but note this article from The Phrase Finder on suggested origins. None of them actually use “the birds and the bees” in reference to the act of marriage. There’s a 1927 newspaper article, but it couldn’t have been the coining of the phrase. Perhaps this is the influence of teachers whose oral instruction permeated the culture.
As for a related phrase, The Word Detective tells us that we don’t know the origin of “naked as a jay bird.” Why pick on jays when they aren’t unclothed any more than any other animal? Evan Morris says maybe it’s because blue jays are stand out among birds, obnoxiously so, in color and volume. On a discussion forum, someone says the folk wisdom he was told has to do with baby jays being pushed out of their nests before they have any feathers. Still, the printed evidence of this fails.
I’ve got a couple ideas; all of which are undoubtedly wrong.
– from Wordnik; “It seemed as if some messenger had gone before him crying his coming, as a jaybird goes setting up an alarm from tree to tree before the squirrel hunter in the woods…” – and so we might have naked as in vulnerable.
– If you look at a photo of a blue jay you see the main body is white – this might, to some, convey the ‘idea’ of naked.
– the jay is known as an aggressive and loud bird; and so naked as bold.
I think you’re getting at the idea Evan Morris, the word detective, suggested, but no matter how plausible your explanation, it doesn’t show an example of the phrase in use. Probably a great example would be a sentence talking about nakedness and using a jay as an passing illustration. Even without the phrase in use, the meaning of the phrase would be established. From what I read, I think this may be a phrase passed on orally, not in print.