Spotted or Common Sandpiper?

The Spotted Sandpiper (Actitis macularia) is very similar in most plumages to the Common Sandpiper (Actitis hypoleucos). There have been several recent records of macularia on the Canaries, including one (17/10/1996) at the Fuencaliente saltpans, precisely where I saw the bird shown in the photos.

This solitary sandpiper has been at its present location for several weeks and has been confidently reported as Actitis macularia by at least one visiting birder. I still haven't seen the bird in flight or heard it call, two important aids to clinching identification, but the general shape, length of tail projection and absence of dark notches on edges of tertials would seem to tip the balance in favour of the Spotted, rather than the Common Sandpiper.

Any comments from birders with experience of the two species would be much appreciated.