Oystercatcher and errr ???

My knowledge of wildlife and more particularly birds is distinctly patchy. My wildlife knowledge and more particularly my knowledge of birds is distinctly patchy. When I first saw this Oystercatcher on the beach I assumed the bird in the foreground was probably a juvenile oystercatcher whose full plumage had not developed. However, when the oystercatcher began to wander off on its own that should have rung alarm bells in my mind. It is only when I came to process the images that I realised that the foreground bird is in fact a redshank as becomes quite clear when you look at my extra which is a close-up of the bird.