OK, time to give up and ask the experts. A friend and I were birding and knitting on the Shetlands last week (Shetland Wool Week falls at the same time as Fall migration). One day we stopped at a little beach near Spiggie Loch, just northwest of Sumburgh. We saw a couple of birds there we're struggling to ID. This is one of them. For a while we were prepared to settle on Water Pipit, although eBird marked it as unusual. Then when my friend posted it on her Facebook page another friend suggested it might be Olive-backed Tree Pipit, which would probably be even more unusual. And of course, it could be something else entirely. :S As you can see, it is in the right environs for a Water Pipit (shallows with lots of washed up and down plant debris), and the colours are hard to tell as with digital photography they seem to shift in different lights, shadows, and surroundings, but the bird did seem yellowish-greenish with brownish streaking and white or creamy wing bars ... at least to our eyes, viewed from some distance (these photos were taken with a 500 lens on a crop body camera, so effectively a 750 lens, and then cropped a bit furtherl on the computer screen).