Redshank (Tringa totanus)

This redshank was on the local shore this afternoon. It is not the usual pose for this bird as you normally see it with its head extended. This one was jerking its head and retracting its neck whilst making a noise. It was almost as if it was choking on something - maybe it was.

I am not familiar with this bird's behaviour so I am open to suggestions but I can add that there was no other bird (visible) nearby so was unlikely to be interaction/display.