So where exactly are all the dead birds?

Okay, so we all know that birds have to die sometime. Also dead birds don't fly... But with all the birds we see in a day, where are their carces? LOL, not to sound morbid but i'm just curious. Aren't you? My friend says that "Stray cats lurk in the shadows and start to make circles under (to be dead) birds, like a vulture does to other dead animals."