I'm hoping he'll get over it. Our other dog, Charlie, was adopted at 3, and he was a deadly squirrel, rabbit, possum, raccoon and woodchuck killer. The chickens were just another critter to him. Repetition and exposure got him to where he just watches them, but if one is loose he will herd it to us or if it doesn't cooperate, he'll hold it down until we come and get it. He doesn't harm the chickens, but if he can catch a rabbit etc. it's toast. At 13, he's not catching many anymore.