I have about 20 mature chicken (2 roosters, 18 hens), and 10 geese. I keep them all in a large yard and let them out during the day. The geese are out at night with a pond and the chickens roost in a coop. This is my second year with them all. Around January of this year, I noticed some feather loss on a few of the hens. I thought it was rooster damage, because the roosters are unharmed. So I put aprons on the hens. That didn't help. Over time, other hens showed the same problem and the first ones got worse! I am now alarmed. So, I wormed them and gave them a round of antibiotics... no change. Some of the hens are getting better and others are getting worse. Egg production is down about 35% (not just due to Winter hours) and I'm stumped by this problem. The feather loss is severe in 4 or 5 hens. I give them oyster shell and feed laying pellets with all the vitamins they need. They have access to grass and get garden trimmings frequently. Bugs, greens, medicine, feed, water and plenty of space! I mean JEEZ C'mon....!