Many songbirds don't just sing to attract a mate; once paired, they often sing with their mate to strengthen the bond. Some species, like the Australian magpie-lark and the plain-tailed wren, perform duet songs so tightly synchronized that they sound like a single bird. What's especially delightful is that these duets can function like avian valentines: a way of saying "you're my chosen one" every morning. In some species, the better the pair's coordination, the stronger and more stable the relationship tends to be.

Quote

“Tomorrow is Saint Valentine’s day,
All in the morning betime.” (very early in the morning.) — William Shakespeare, Hamlet

Fun Fact

The oldest known written Valentine message dates to 1415, when Charles, Duke of Orléans, wrote a love poem to his wife from the Tower of London. Parts of that message still survive today in manuscript collections.