Thursday, 23 June 2011

Overlooked, but over here?

Field test: Semipalmated and Ringed Plovers are famously hard to identify. Have a go at these two for starters ...
In terms of low detection rates, few shorebirds in the Western Palearctic beat Semipalmated Plover. This is an atypically rare wader, with, for example, just two British records and one in Ireland. Why atypically rare? The last British individual of this migratory Nearctic species - which is very numerous on passage on the east coast of North America - was at Dawlish Warren, Devon, from April-September 1997 and again from March-May 1998; compare that single occurrence with the 1997/98 WeBS figure of 23,000 passage Ringed Plovers (see Is a 1:23,000 ratio really representative of the true status of Semi-p?

Juvenile Semipalmated Plover, Corvo, Azores, 13 October 2007.
It certainly doesn't compare favourably with the strike rate in the Azores, the only regular location for Semipalmated Plover on this side of the Atlantic. I've seen it there on numerous occasions in three different islands, and on Terceira it is often possible to observe the species alongside lookalike Ringed Plovers in autumn. Despite limited observer coverage, no fewer than 17 Semipalmated Plovers were found in the archipelago in 2010 alone, hinting at the true number that must be reaching mainland Europe, and there have now been about 200 records in total in the islands.

Juvenile Semipalmated Plover, São Miguel, Azores, 10 October 2007.
Ringed Plovers are, of course, more common in the Azores than Semipalmateds, though the latter can sometimes outnumber the former on passage (see the Birding Azores website for the stats). The wintering Ringed Plover population is said to be as low as under 100 birds, so perhaps the ratio on the Azores, where one or two Semipalmateds sometimes winter, is more like 1:75, or even better?

With that in mind, the challenge for birders in Britain, Ireland and continental Europe is to look harder for this species and find those missing Semi-ps. Having twitched that Devon bird back in 1997 and since seen and found a few on the Azores, I feel like I'm at last getting a better feel for the species. For starters, when heard (and learnt!), the upwards-inflected chu-wee call is quite distinct from (and higher in pitch than) Ringed Plover - and diagnostic.

Jizz-wise, the slightly smaller size and proportions of Semipalmated give it a touch of Little Ringed Plover, while the famous 'white wedge' gape feature of juveniles, first noted by Killian Mullarney, the thin yellow orbital ring and the toe webbing (when visible) are also useful. Other subtle characters such as relative differences in bill size, breast band and supercilium can also help, but I still find some birds more obvious than others (and feel free to disagree with any of the IDs here - all self-found birds photographed/filmed in the Azores). The video clip below, shot in May this year on Terceira, perhaps gives a better feel of the species' jizz than still images can:

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