The mites that you saw are red mites. You can not look on your birds in daylight and find RED mites. These mites live in the cracks and joints in a wooden coop or hen house during the day. Since red mites lay their eggs in these same cracks and crevices it is impossible to get effective long term control by trying to root them out with a pressure washer. At night the RED mite comes out to prey on your chickens by sucking their blood. After a RED mite feeds it looks red from all the blood it has just eaten.
I prefer a little Permethrin mixed with old motor oil and then dabbed or painted on all wood joints and cracks in the hen house, including the roost poles. Permethrin is an organic pesticide and is perfectly safe to use on chickens' premises when used in accordance with the manufactories' recommendations. It is even prescribed for use on human infants to combat things like head lice and scabies (a cousin of the scaly leg mite)
A good side effect to using Permethrin is that it is also a mite and insect repellant. There is also no egg withdrawal period with Permethrin like there are with Sevin 5% dust or 50% wet able powder. Permethrin can also be used as a body drench of tank dip solution. Do not use or dispose of Permethrin around lakes, rivers or streams because it will kill aquatic life deader than 4
o'clock. This is why I use old motor oil as a carrying agent, it helps prevent the Permethrin from being washed out of the cracks and crevices of the coop.
