Yesterday afternoon when I checked the nests,there were no signs of eaten eggs,so I sacrificed one and injected blue food coloring in it and put it in one of the nests.I hid out and noticed one hen in a nest kind of pecking at the eggs,so I thaought"ah ha! that's probably the one." I took all the eggs but the decoy egg out and left for awhile. When I went back about 10 minutes later,I caught her on the side of the nest,egg half eaten,and with bits of blue egg shell on her beak! I clipped her top beak and marked her with food coloring. Hopefully she will not be able to break any more eggs,but if she does,I will know which one she is and remove her.