I am new to this forum, but I was looking at some pix of small insects that seem to be bothering some chickens. There was a pix of some bugs on a lid of some type, I guess. First, where is this chicken? In what part of the country? In the USA? No location is given with posts, so I am in the dark. However, these blood-sucking insects look a lot like nymph ticks. Has anyone thought to take some of the bugs to your local extension for correct ID? If they are in fact ticks, they can do severe damage to poultry due to blood loss. The loss of feathers is probably due to the bird scratching in an attempt to remove the ticks. I assume the birds are free-range?
I would try Neem oil in a carrier oil...olive, grape, corn, canola oil. 25% Neem to 75% carrier oil. Mix well Neem oil goes solid at temps below 74 degrees, so keep the mixture warm prior to application. If you can, spread the oil on the affected area. Try to remove any ticks (?) attached to the skin. There are also something called "stick tight fleas" that might be the infestation. I have not personally seen these bugs, so I can't ID them, but they will also make birds sick due to blood loss. Seems ducks don't have so much of a problem if they have access to swimming areas. There are several diseases that affect chickens, you might want to find a good book at the library and check out the symptoms to see what is the issue rather than to try to treat them before you know what the issue is. DE is good for keeping vermin off birds, but not so great if there is already an infestation. Neem oil will work best for removing any lice, mites. I have never seen a tick on any of my birds and I had many turkeys, ducks and chickens.
If you suspect an infestation of vermin in the coop, completely clean out the coop, nesting boxes down to bare. Scrape roosts, a wire brush works well. Clean any areas of heavy build-up. Sweep clean. I have used a shop vac to clean out corners and crevices. This is a serious house-cleaning job. If you have any questions regarding disease in the house, use white vinegar and hydrogen peroxide...after a good housecleaning, spray vinegar to the point of drip, the follow with a spray of hydrogen peroxide. Do not mix the two together, it is similar to mixing bleach and ammonia and will give off killer gasses. I used a one gallon pump up sprayer. Be sure to get under roosts and inside nest boxes. Allow to dry. The spread DE on the floor and bottom of any areas in the poultry house. Sweep the DE into cracks. Use clean bedding on the floor and nesting boxes...sprinkle some DE on top of the clean bedding.
If you have lice or mites, you have to PAINT THE ROOSTS AND WALLS WITH OIL to smother the insects. Old veggie oil (DON'T USE RECYCLED COOKING OIL!!!) painted on all surfaces will smother any insects. Then spread DE as I have suggested. Be sure you have FOOD GRADE DE, pool grade is not the same.
Set up some dust bath areas that are protected from rain or wetness. Add plenty of DE to the dust bath. I have found that elemental sulfur, wood ashes and DE make a nice dust bath with clean sand. The dust baths should stay dry or they will become ineffective.
BTW, DE is very good for intestinal parasites. I have been very successful at worming my flocks with DE in their foods. Internally, it doesn't have to be dry. I have mixed about 1/3 cup DE into four quarts of layer pellets as a remedy. Feed this mix for several days (3-4 days), then wait two weeks and feed the mix again. If you are not feeding dry feed, you can mix it in with any foods. wet or dry.
I was Certified Organic for poultry, grains and garlic for nine years. These remedies in this post are all organically accepted and will not harm poultry.