When I first heard the loud recorded bird cries outside the 24th Street BART station, I assumed it was an artwork, songs installed by artist for a while. Around here you can do a vast number of art things with official okay if you're okay with them being temporary.

I heard them as tropical birds, pictures a rain forest instead of concrete and brick. The newspaper told me it was officially art; it was a scare the pigeons away to reduce pigeon droppings deal.

The cries were the cries of predator birds that might eat pigeons, the cries they make when swooping for the kill and meal. I think it nature you wouldn't hear that many one after another, on and on. I haven't heard hawks, but I've seen them, and they seem to work one at a time.

I liked the nature noises. I kept hearing them as rain forest actions though they weren't.

I moved and didn't go to that BART station for a while. When I came back, the bird noise was gone. I heard the silence it left, amidst the car noise. I guess hearing that silence was a sort of artwork too.