I have one really determined EE, even when I kept clipping her wing until I was afraid to clip anymore. If you can put a roof/fencing on your chicken pen, that would be good. Do the birds go in the front yard? My GSD, on a tie out, was able to catch chickens because it was somewhat close to a wall on one side. The EEs were attracted to the danger, I think...or just really stupid. I was home both times when it happened, so the birds didn't get hurt. The first time, I thought that was a freak accident. The second time, I realized that he was learning to corral the chickens and getting them to react and move the way he wanted. GSDs are herding dogs, after all.
Dale-Ann
Dale-Ann