I went through the same thing when I first started keeping laying hens.something went through my (chicken) wire and killed five of my hens that had been laying for two weeks or so,I had raised them from chicks,First thing I done was totally wrap my pen with hardware cloth,made a skirt 18 inches wide around the base of the pen with steel wire to prevent dig ins,next I ran a very powerful electric fence around the bottom and another strand about 12 inches higher,ran electric fence up and down each post and around the top of the pen,put a steel wire cover over the top of pen,totally enclosing everything,Next I purchased 4 of the niteguard lights,two havahart steel wire traps,two boxes of 22 ammo and started trapping raccoons,I know raccoons have to eat,,but not my chickens,thats been 3 years ago and I have not lost another bird plus I been giving the raccoons hell,and also saved a lot of my sweet corn that raccoons also love to eat and destroy..Good luck