More on ID of tricky ones
Guillermo Rodriguez Lazaro
Hi Yoav and Martin,
I saw your post about the Israeli vulture in the Birding Frontiers blog and thought that perhaps I could provide some light about this bird.
The second photo (underparts) shows an indisputable Griffon (repeated above), definitely ruling out Rüppell’s The complete absence of white edges in wing coverts (not only GCs but also in MCs) is diagnostic. Other features which don’t indicate Rüppell’s are the shape and color of the axillary feathers, absence of white edges in UTCs, strong contrast between black GCs and much lighter MCs, etc… I attach a photo of a classic erlangeri adult from below from northern Ethiopia for comparison.
So, as pointed in your post, only the upper parts resemble Rüppell’s, I think that mainly due to the presence of two-rows of dark wing coverts, a feature typical of Rüppell’s (which usually has present 2-3 rows). Additionally the bird’s overall colour is perhaps unusually greyish for Griffon, but this species presents a high variation in this trait and I feel it isn’t a strong feature to discard Griffon. In my opinion, your bird doesn’t fit well one of the striking “pale morphs” Rüppell’s which from time to time are observed in NE Africa (it’s too patterned and browner above), so we should compare with the more classic erlangeri adults.
In both Griffon and Rüppell’s all wing coverts present a dark feather center with a pale edge. In Griffon, only the greater coverts present an extension of black large enough to be visible, whereas in the median coverts the dark part is very limited (due to the broad pale edge) and it’s usually not visible. In Rüppell’s, the pale edge is much finer and thus the dark centre of the feather is exposed and very obvious in the upperwing. However, I’ve found that a few Griffons (Spanish breeders at least; I’m not sure if it is an individual characteristic or just the result of a certain state of moult, though the first option is more likely since these birds seem to present also more patterned scapulars) can show two rows.
In my opinion, your bird is one of these odd Griffons. Detailed analysis of the upperparts pattern shows that the feather edge of the second row (median coverts) is too broad, and concolorous (cream coloured) with the rest of the wing, whilst it is usually whiter and thinner in Rüppell’s. The wing looks very uniform and with the characteristic griffon-colour of the species, instead of the more browner/greyer appereance of erlangeri Rüppell’s. I also attach one photo of an adult erlangeri (again from N Ethiopia), in which these features are evident.
Taking into account these points, I don’t find consistent reasons for considering a Rüppell’s here but just a slightly unusual Griffon. Other characters also support this id, eg the bird silhouette and the blue skin around the auriculars which provides the characteristic Griffon head pattern.
The option of a hybrid is, in my opinion, even more complex: as far as I know there aren’t proved records, though there is at least one suspected individual from Spain which certainly ticks all the boxes:
Apparent hybrid click HERE
Hope these comments are interesting for you and help to clinch the id.