Common or Canary Islands Chiffchaff?
During a birding session at the saltpans in Fuencaliente, on the evening of December 19, I was surprised to spot the bird shown in the present post. The most ubiquitous and abundant passerine on La Palma is the endemic Canary Islands Chiffchaff (Phylloscopus canariensis). But what struck me about the individual shown here was its much greener, more contrasting plumage, its lack of buff tones on the flanks....and the fact that it was found at a location where I had never seen a single Chiffchaff previously, despite frequent visits to the site.
The bird was first observed foraging on the ground amid the sparse, coastal scrub on the inland side of the entrance path, and was shortly rediscovered on the stoney banks of the saltpans themselves, where all the pictures were taken. The only passerines which frequent this part of the island are the Atlantic Canary (Serinus canaria), Berthelot's Pipit (Anthus berthelotii), Sardinian Warbler (Sylvia melanocephala) and the scarcer Spectacled Warbler (Sylvia conspicillata). So here was a case of an unexpected species doing unexpected things in an unexpected area...
The photograph above enables the tertials and primaries to be appreciated: the length of the projection appears to correspond to a Chiffchaff. But are the greenish tones on the upperparts, and the patches of lemon-yellow on the flanks typical for a Canary Islands Chiffchaff?
I have been through all my fieldguides and checked photographs on the Internet. To add to the difficulty there is, of course, an Iberian Chiffchaff (Phylloscopus ibericus), and three subspecies of Common Chiffchaff have been recorded in Macaronesia, the nominate collybita (W and C Europe), abietinus (N and NE Europe) and tristis (Siberia).
If bill-length is diagnostic, when seen from the above angle, this specimen appears to conform to the proportions for the Common, rather than the Canary Islands Chiffchaff. Unfortunately, the bird emitted no calls or song to aid identification.
The last photo (above) shows the lemon-yellow tones around the vent and underparts of the tail.
Any comments regarding the identity of this specimen would be much appreciated. In the meantime, I plan to consult the ringers and other experienced passerine observers at rarebirdspain, and will post their verdict shortly.