Thursday, 20 September 2012

Short fall

Juvenile Short-billed Dowitcher at Lodmoor RSPB, Dorset, today - Britain's second individual.
There is a small but noteworthy list of Nearctic shorebirds that, for one reason or another, appear in Britain far less frequently than their numbers, distribution and migratory habits might suggest. Semipalmated Plover is one such species that I've blogged about before; another is Short-billed Dowitcher. More numerous on the eastern seaboard of North America than Long-billed Dowitcher, Short-billed is paradoxically far rarer than that species in mainland Europe. Yet on the Azores, prior to this year there were 24 records of Short-billed and just 10 of Long-billed, with two further records of unidentified dowitchers. Compare that ratio to Britain, where by the end of 2011 there was one accepted Short-billed compared to 209 Long-billed. This may be partly accounted for by Long-billed's breeding distribution extending into Siberia, so that some of our birds arrive from the east as well as the west, but that isn't the whole story.

The bird was always rather distant but showed well at times on the west scrape.
Another factor must be identification. It is notoriously difficult to separate the two species, especially for British birders who inevitably have limited or no field experience. The one previous British record of Short-billed dates from autumn 1999, when it was seen in both north-east Scotland and Teesside: the second and third, found this month in Dorset and Scilly respectively, were both initially thought to be Long-billed Dowitchers until photographic evidence confirmed otherwise. How many others might have been wrongly assigned to the sibling species, especially in less distinctive non-breeding adult plumage? I think there is a mentality in Britain that dictates any dowitcher here is a Long-billed until proven otherwise - a view perhaps borne from a past review which discounted some older records of claimed Short-billeds, before the ID criteria were better established.

Spooked by a Black-headed Gull, the bird reveals useful feather detail on the upperwings.
The bird in these images is the Dorset individual, which I caught up with twice today in morning and afternoon visits to Lodmoor RSPB - a major 'grip-back' 13 years on from having missed the 1999 bird when it was on Teesside (I arrived the morning after it departed ...). Scope views of today's bird were good, but photographically it was always too distant for detailed portraits. These heavily cropped images still give a reasonable feel for Short-billed Dowitcher in juvenile plumage, with its distinctive internal markings on the tertials and greater coverts being the single most important distinction from juvenile Long-billed. Several interested members of the public stopped to ask what we were looking at, and left somewhat bemused at the fact that this bird could be described as a short-billed anything!

The obvious notching on the tertials is a giveaway for juvenile Short-billed.

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