As for peregrine falcons, I recently had the pleasure of watching one "disturb" a bunch of waterfowl at a desert marsh recently. I knew it was there too even before I saw it. Once it's spotted by all the local birds (such as yellow-headed blackbirds, red-winged blackbirds, and assorted duck species), the entire marsh lets out a "collective scream," so to speak.
It's hilarious. You know something is horribly wrong and then you look up and see what's causing all the commotion. Invariably, it's a peregrine falcon, or as I like to call it -- a waterfowl's worst nightmare!
Lucky you having those Yellow-headed Blackbirds! I’ve never seen one before as they are rare in Central Massachusetts, but they are just gorgeous birds.
The only birds the Peregrines get in the city are normally the pigeons but I’ve seen the falcons at Plum Island and you are right in the fear they strike in waterfowl. It went from peach and quiet to bird hysteria. So fun to watch though!