Thursday, 7 July 2011

Wood Sandpiper and Lesser Yellowlegs – a cautionary tale

Wood Sandpiper (Rainham, Greater London, 14 August 2010). With its obvious supercilium and shorter bill, Wood Sandpiper is unlikely to be mistaken for 'Lesser Legs' in typical field conditions. © Dominic Mitchell
Lesser Yellowlegs (São Miguel, Azores, 15 October 2007). Seen well, this American species is distinctive. But at a distance of 500 m, against the light? Read on ... © Dominic Mitchell

By Keith Vinicombe

With the advent of modern field guides and birding magazines, it is easy to assume that we have the identification of most rare and scarce birds well and truly sussed. But every so often we hear of what appear to be, on the face of it, elementary mistakes being made, even by experienced observers.

This was brought home to me on Tuesday 28 June during a routine visit to my local patch, Chew Valley Lake in Somerset. An adult Wood Sandpiper had been seen there the previous evening, a rare June sighting in this part of the country. I relocated it during the afternoon at the opposite end of the lake, but the views were distant and it disappeared for long periods behind a stony spit, so I drove around to Herriott’s Bridge at the south end of the lake. I soon relocated the bird but it was still about 500 m away and, frustratingly, against the light. It was impossible to make out any plumage detail and, more importantly, leg colour. It consequently appeared an amorphous, featureless bird with pale legs.

However, as I squinted down my telescope, I gradually began to wonder if it really was a Wood Sand. Most obviously, it had very long legs, with particularly long tibia (between the ‘knee’ and the body). It was also long-necked and long-billed and, even more worrying, it showed a long, tapered rear end. It also strode around, feeding more like a shank than a sandpiper.

As I continued to watch it, I became more and more convinced that it had to be a Lesser Yellowlegs, and I tried phoning others who I knew were at the lake. Eventually, Richard Mielcarek appeared and we agreed he would continue to watch it while I tried to get closer views from a different angle. In best commando style, I managed to creep down a ringing ride through the reeds and set up my scope close to the spit. Frustratingly, the bird had vanished but, after a few minutes, it came striding round the corner. My heart sank: a bog-standard adult Wood Sandpiper (Wood Sand is in fact my favourite bird, and I have never before been disappointed to see one!).

Wood Sandpiper (location unknown, 22 August 2006). © Steve Young
I phoned Richard and returned to the bridge. He told me that he too thought that the bird looked promising for a ‘Lesser Legs’, as did one or two others who had by then also appeared. I should add that the reason why the bird looked so slim, elegant, long-necked, long-legged and so attenuated at the rear, was that it had sleeked down its plumage in the afternoon heat.

The point of the story is to reiterate the obvious fact that, no matter how much you think you know, you can always be thrown by birds seen in difficult circumstances - in this case long distance and bad light – and that misidentifications are not always the result of incompetence by the observers.

Episodes like this are, however, instructive, emphasising the need to make sure that you obtain decent views of a bird before you make that all all-important phone call to the bird information services. It also illustrates a human trait that has always concerned me: in the absence of strong evidence to the contrary, once you have set your mind on a certain route, it is in fact very difficult to stop, change your mind, and go down a different one. It also shows that even experienced birders can be confused by standard birds seen in less than ideal conditions – a lesson for us all!

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