One hen less!

Something had plucked and half eaten one of the brown hens today, whilst all the rest were hiding in the hen house looking worried. This is the pile of feathers left behind. 
We haven’t seen this before. We’ve had hens disappear, hens run over in the road when they made a bid for freedom, and hens with their heads bitten off and taken away (I think the last one was pine martens)and bodies left behind,  but not plucked like this.
Could it be a hen harrier? Mr F has set up the wildlife camera!