Semipalmated Sandpiper (Calidris pusilla)
The bird's bill is certainly straight and shortish, but seems a little longer than that of the previous pusilla recorded at the same location four years ago (see Oct 2 2010 blog post for details). The legs of the present bird are not pure black, but tinged dark olive, with the partially-webbed inner and outer toes clearly visible.
In addition, the very short primary projection beyond the tertials can also be appreciated. The only other Calidris with similar webbing is the Western Sandpiper (C. mauri), but mauri has a thinner and longer bill which is slightly decurved.
Below are a couple of shots allowing size-comparison with the Dunlins present at the same location.
Above and below: C. alpina and C. pusilla.
According to Rare Birds of the Canary Islands by Eduardo García-del-Rey and Francisco Javier García Vargas (Lynx Edicions, 2013), to date, there have only been 5 records of this Nearctic wader on the Canaries:
La Palma n = 1 24/09/2010
El Hierro n = 1 14/10/2011
Tenerife n = 2 18/10/1995 and 03/05/1997-05/05/1997
Lanzarote n = 1 01/11/2008-04/11/2008
This sighting will be forwarded to the Spanish Rarities Committee in due course.