All of my little flock of five hens have had this recently, I discovered, about two months ago. I unroofed several of these scabs, without any pus or purulence noted. This made me think that I was performing unnecessary surgery on my hens.
I am a wound care physician, and I am not a veterinarian. I cannot claim experience here except for with humans.
So, I researched everything I could find, being a "human doctor", wanting to make good clinical decisions about my girls without putting them through pain.
I learned that this condition usually results from Staph (Staphylococcus) infection. Well, I should be the expert here, since I am an Infectious Diseases physician, and I know that Staph can do anything in humans. The point here is to realize that Staph can cause anything from a tiny pimple to a life threatening infection. But you have to use your judgement as to how bad the infection is (or not).
I looked at my girls feet and decided that most of them did not look swollen or red, and that they were not having any trouble walking. I changed out their roosts for fresh wood since I read that this may be a culprit. I contemplated painting their feet with betadine but did not do it.
Now 2 months later nothing has happened, except that the scabs are falling off or becoming smaller.
I keep watching each hen daily for the red swollen foot I should operate on. This is because unroofing a scab can actually expose an open wound to infection, and I choose not to do this.
I hope this helps you guys because the scabs did really freak me out initially.