Peregrine Falcon (Falco peregrinus) ?
From a distance, through my car window, the first thing which attracted my attention was the large size of this bird: roughly as big as a Common Buzzard (Buteo buteo), the only other raptor of similar proportions found on La Palma. The location was also appropriate for the Buzzard, close to a main road in an area where the species is regularly seen. On closer approach, however, the perched bird of prey revealed itself to be a Falcon: but surely too big to be the resident Barbary Falcon (Falco pelegrinoides)? I parked, and managed to get the first photos from inside my car...
These shots are almost against the light: even so, the plumage looks much darker than in typical Barbary Falcons; the moustachial stripe is also wider, and there appears to be no hint of rufous or pale patches on the nape.
The fine barring continues all the way up the breast as far as the neck, where some scattered streaks can be appreciated. There could be a slight off-white tinge to the underparts, but it is difficult to assess the precise shade in these photos. The powerful, broad wings, and the robust body and head would seem to indicate Peregrine, rather than Barbary...
According to the Field Guide to the Birds of Macaronesia (Eduardo García-del-Rey, Lynx Edicions, May 2011), the Peregrine Falcon is a vagrant to the Canary Islands (Tenerife, Gran Canaria, Fuerteventura, and Lanzarote).
Rare Birds of the Canary Islands (Eduardo García-del-Rey and Francisco Javier García Vargas, Lynx Edicions, June 2013), states that the subspecies of Peregrine so far recorded on the Canary Islands is suspected to be calidus. However, the only records cited are from Tenerife (n=7) and Lanzarote (n=1).
Any comments as to this bird's precise identity would be appreciated.
Thanks to the help of a number of Canary Island birders with experience of the Tagarote, or
Barbary Falcon (Domingo Trujillo, Beneharo Rodríguez, Francisco Javier García Vargas and Juan Sagardía), the identitiy of my bird has been settled: it is in fact a female Barbary Falcon, and not a migrant Peregrine.
For future reference, it is worth bearing in mind that pelegrinoides shows considerable variation in plumage tones, size of rufous patches on nape (if any), and width of moustachial stripe - amongst other features - as well as differences relating to age and sex of individual birds. So...quite a complex species, which doesn't always match descriptions and illustrations found in standard field guides.
Of course, being the only resident falcon on the Canary Islands this species can usually be safely identified "by default": however, large, dark individuals during autumn or spring migration periods merit close attention.