They look like Red Mites. :( Red Mites live in the cracks in wood of your coop. A good spraying with liquid Sevin will do the trick. Dust your birds & repeat the whole process in 10 days.
Ideal Hatcheries has Houdans. That is where I got mine.
Gretchen--Yoou Frizzle baby is adoreable!
You can see my Frizzled Roo at:
http://poultryone.com/photo/main.php?g2_itemId=4105
http://poultryone.com/photo/main.php?g2_itemId=4105
I cannot figure out how to upload the pics of my roo!
His name is "Partybird" & you can see him here!