I heard guinea fowl eat a LOT of bugs.
Yes they do. The best tick control you can get. Great for the livestock area.
What about chickens? I was told they eat fly larvae from manure.
Yes they will, as well as un-digested grain that would normally just go to waste. (saves on chicken feed bill too.)
I plan on getting chocolate, bourbon red, and/or midget white turkeys. The websites I was on neglected to mention what the poultry DIDN'T eat.
They'll eat bugs, grain & seeds, frogs & toads, Mice, and just about anything else. The only thing that I know for sure that they won't eat is what they can't see, or is to big to swallow.
All of the above like and eat grasshoppers. Young ducks are good at chaseing and eating them, but slow down when grown. (Then would be a good time to have them for dinner)

Pheasants are the best at eating grasshoppers, but hard to keep around close. However, hand raised jumbo pheasants (if you can find any) will hang around close about like the guineas. The ones I had would eat right out of my hand.
Hope that answered your questions.