Snakes. I've lost chicks and pullets to them.No matter what i've done,they've managed to sneak in.My mothball barriers didnt stop them neither.Chicken snakes,red and yellow rat snakes love chickens.I had a 5 foot long chicken snake drag my full grown Buff Orpington off her roost in the middle of the night and dragged her out in the pen trying to constrict her.If it wasnt for her screaming,I wouldve never known what happened.Needless to say,I quickly dealt with the snake after it bit me several times! I brought poor Buffy in the house and inspected her closely and fortunately there wernt any bite marks.I returned her to her house and put her on her roost.The next day my faithful Buffy had layed me an egg, even after all what had happened.