Tuesday, 10 September 2013

Siberian sandpipers put on a show

A somewhat flat start to the day, with high cloud and a hint of autumn chill, found me sat in one of the hides at Cley, scanning the muddy shallows for waders. Along with an occasional godwit, a scatter of lapwing and a few dozen ruff were two small groups of more delicate waders – one numbering four individuals, the other five. These were curlew sandpipers, a species that breeds along the coastal margins of northern Siberia and winters widely, from West Africa to Australasia. It is a passage visitor to our shores, with larger numbers passing through in autumn than in spring.

Curlew sandpipers are, in some respects, similar to dunlin, the latter species providing a useful starting point when attempting identify many a small wader. Slightly larger in size than a dunlin, these curlew sandpipers had a more upright, somewhat elegant, stance that was clearly evident as they fed in the shallows. These were all juvenile birds, with clean white underparts, a smudge of colour on their breasts and nicely marked backs. Later in the morning a good-sized flock of dunlin dropped in and soon the two species were feeding alongside one another, providing the perfect opportunity to underline the differences between the two species. When seen together, the longer, thinner and more curving bill of the curlew sandpiper is clearly apparent, although it is not necessarily a useful identification feature when viewed in isolation.

The numbers of these delightful little birds passing through our shores represents a tiny fraction of the global breeding population and probably derives from those birds nesting at the western end of the breeding range and wintering in south-west Europe and West Africa. Passage numbers, which peak in September, tend to fluctuate from one year to the next, with occasional years when very large numbers pass through. Numbers show some correlation with how successful the breeding season has been but are more strongly influenced by autumn weather conditions. A run of easterlies over Scandinavia and the Baltic during autumn passage, sees more individuals reach our shores, which is good news for us birdwatchers. Most will be seen on the coast, at places like Cley and Titchwell, so now is a good time to go and find them.

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