Telling Knot and Dunlin apart is tricky, but look out for some tell-tale signs
Telling both birds apart in a crowded estuary may be a challenging task, but it’s worth the time and effort
HOPEFULLY EVERY BIRDER has experienced arriving on an estuary at low tide and being faced with a seething mass of moving bodies – waders all feeding busily on the ooze. It’s an impressive sight, and there is usually a delightful aural accompaniment of the unfettered wind and the urgent calls of the birds, from the shouting Oystercatcher to the euphonious Curlew ‘bubble’.
And then, of course, comes that sinking feeling: you’ve got to identify this lot. You aren’t really compelled to, but you feel you should try, so you attempt to get comfortable and pan your binoculars or telescope hopefully across the estuarine shopping mall. You feel better when you see the tri-coloured Oystercatcher, the oddlypatterned Turnstone and the Curlews towering over everybody. But after this, on most British estuaries at least, a seething mass of predominantly grey mites dominates the mudscape. You can tell they are waders, but which ones? Your book is full of Redshanks, Spotted Redshanks, Grey and Golden Plovers, Knots, Dunlin, Little Stints and a whole wealth of rare Americans. For a while, you study hard and then, somewhat defeated, you decide that you will simply let the scene sink in and enjoy it. Of course, it is possible to decipher the many different wader plumages and shapes, but it takes time and experience. I was highly amused to read recently in a thoroughly learned book that the Knot, even in non-breeding plumage, was “unmistakable when in company with its smaller
congeners”. That’s a load of rubbish. The Knot is eminently mistakable for a Dunlin, and it is entirely appropriate that it should be so. It would not be going too far to say that it is biologically appropriate that Knots and Dunlin (and Redshanks and Grey Plovers) should look alike. Waders are grey and plain in winter for the same reason that warblers are brown or olive-green; the plumage affords them a degree of camouflage within their environment. Waders are necessarily mud-coloured. If you do take the time, it is fun to distinguish them. The plump-bodied Grey Plovers have star-like spots on their upperparts, plus a short, thick bill and large eye. Redshanks show off their eponymous bare parts and are middling in every way: middle-length bill, middle-length legs, middle-sized. Knots and Dunlin are much harder to tell apart. After a while you can appreciate that the Knot is slightly larger and a little plainer. It looks slower in movements than the scampering Dunlin and it seems to lean over more when it is feeding, but the margins of identification are thin. But the fact is that, on the estuary, Knot and Dunlin are very similar, and not just in appearance. Their daytime routines are almost identical, because these are determined by the tide; at high tide they roost, at low tide they feed, and on a rising or falling tide they revel in newly exposed or covered invertebrates. The ‘ground’ over which they feed can be exactly the same, and they will often gather food in much the same way. Take a look at a description of the feeding methods and it isn’t easy to discern much difference; Dunlin and Knot both “peck” and they both “probe”. As far as probing is concerned, Dunlin “stitch” and Knot “plough”. A Dunlin will sometimes feed by a series of rapid insertions of the bill, as if it were sewing. And as for ploughing, the Knot will insert its bill into the mud and move forward for a few centimetres, making a furrow in a bid to touch an edible object. The fact is, therefore, that they live almost interchangeable lives on the mudflats of Britain, for a good six or seven months of the year. Combined with their similar appearance, you could guess that almost everything else they do is similar. But you would be mistaken.
Of course, it is possible to decipher the many different wader plumages and shapes, but it takes time and experience Winter Dunlin
On the estuary, Knot and Dunlin are very similar, and not just in appearance. Their daytime routines are almost identical Dunlin on the move