Hi--We started raising backyard chickens a little over a year ago. We bought a big coop with a rooster and 10 chickens. We successfully free ranged them during the summer. We added to our group with pullets and some we incubated the next spring. They all seemed to get along and we got rid of the extra roosters. We integrated them seemingly successfully and they all free ranged together this past summer. The first rooster died (we don't know how old he was) and he had one day of difficulty breathing and died that night early this fall. We got a new young rooster and once they were used to each other we let them free range together. We then found a dead chicken with the head and neck pecked under a storage shed where they liked to go. Then we started having a rash of hens disappearing, some at dusk and heard wings flapping (maybe an owl?). The always went back to the coop at dusk and we would go out and lock up the coop when the hens were all in. We thought maybe the hens were being picked off because the trees are bare... We have now increased the pen size and put netting over the top to keep out predators like owls and hawks, and put them all in together. Then we had dead hen in the pen with its head and neck pecked. We thought it was the rooster as he would peck at hens who didn't want to cooperate with him. So we put him in a separate pen and things went well for awhile, then the last two days we had two more hens found dead with their heads and necks pecked with the rooster not able to get to them. We think the pens are safe. There is plenty of room, we feed them pellets and scratch and sometimes snacks of bread or vegetables. So is it possible one of the older hens has become a killer chicken? Soon we will have no hens left and then I guess we will know which one is the culprit. We have separated out the rooster again only because he still seems too aggressive even if he is not a killer. Would appreciate any input. Thanks.