Every morning I wake up at 4:30 and listen. Within a minute or two the first bird begins to sing. Then another joins, then another until there is a swell of loud and joyous choral rapture. The birds sing their melodious and varied tunes; they whistle and chirp and tweet and fill the woods with happiness. After an hour, the songs diminish, and the birds, well satisfied with their morning hymns, go about their day.
It is said, of course, that birds sing to woo mates and to defend, or maybe announce, their territory. These songs bring such happiness to me I can't imagine they aren't born of the happiness of the birds. Birdsong can't be just mechanical, no-emotions-attached. honey-look-at-me stuff. It is beauty! It is music! It is joy!
Scientists don't like to talk about happiness. They call such attitudes anthropomorphism. Literary critics call them the pathetic fallacy: just because we feel in sympathy with a bird's song doesn't mean the bird is expressing what we would feel if we were singing like that.
But if even fruit flies can feel depression (fruit flies?), then it seems reasonable that birds feel joy when they sing. (And, yes, scientists have determined that fruit flies can die of depression, or something like it. Check it out on jpr.org or in the Guardian.)
It would also be reasonable to speculate that if fruit flies can be depressed, so can birds.
Birds learn singing from their parents, so one could postulate a scenario.:
"You must sing, little one."
"Mommy, I don't feel like singing. I hear chain saws in the woods."
How long will the birds fill our woods and fields with the happiness I hear every morning when I wake up?