I have lost about 30 chickens to predators in my life. One was my favorite 7 yr old hen I kept in what I thought was a predator proof barn and I kicked myself over and over again for not realizing all the possible ways they could get in. Raccoons were the biggest predators we dealt with because they can climb and squeeze into anything. Hawks are second. Almost lost a broody hen with a clutch of babies and a Mallard duck this past summer to hawks. We had to make fully enclosed pens for them all. We also had a couple birds taken by a fox.