My guineas make the most noise when a hawk, eagle or owl is overhead. They are more vigilant than my chickens. They fly extremely well. that can easily fly up 20'. They like to roost much higher than chickens. I keep mine with the chickens, feed them the same feed and at night they all return to the coop just like the chickens. They are wilder and I only find about 20% of the eggs.
They will let you know when a predator (real or perceived) is around with a racket that could wake the dead! It doesn't bother me and my neighbors are too far away to hear them.
My ducks are slowly learning to pay attention to the guineas when they go crazy.
Both my chickens and ducks have learned to heed the warning call of my flock of guineas. But the only problem is that they're not always in the same location as the others, since they love to roam my 20 acres in search of bugs. My guineas have chased fox, coyotes and dogs out of my barnyard - it's hysterical to see them in action - they'll surround the predator and start squawking at it until it gets scared and runs away!! They've also noticed hawks sitting up in trees.....just waiting for the opportunity to swoop down on one of my chickens......but they've never really chased one away - just alerted the others there was danger lurking.