Going to the coops this morning to open up and then poo-pick, I first found a blood puddle and spatters on the roof of one, and then found a few blood-stained shavings scattered around inside all three. I don't know what went on yesterday - I was out most of the day. The flock is not unusually nervous or tight-knit so I don't think it was a predator, which is one obvious explanation for the blood drawn, so I assume with the season the sap is rising in the boys, and they fought more strongly than usual; somebody drew blood, and whoever was on the receiving end was attempting to find refuge in a coop, and presumably failing in all three sequentially. Normally they don't try to hide inside, but run off into the bushes and stop as soon as their pursuer stops giving chase.
I got photos of them all just now and there's nothing conspicuous to explain who did what to whom; all are working together as one flock, Chirk is clearly still the dom and the other 3 the subs. Anyone with any other suggestions to unravel the mystery?