Three years ago my dad was hunting Norhtern IL and was working a group of toms when out of the blue he hears a very loud and weird noise that he had never heard before. It continutes for some time (he said it was terrribly loud) and finally after about 20 minutes he caught movement. Thinking it was a turkey he got situated to make a shot, then he saw a big peacock checking him and his setup out. It continued barking or whatever the hell they do, but he said that he never heard another tom gobble once the peacock started making noise. He said they were so fired up before that the only thing he could think of is that the peacock call scared them more than anything.