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An interesting juvenile Shag that I observed at the back of Rosslare Harbour just before dusk yesterday. The very extensive white on the throat, foreneck and underbody, as well as the much more prominent (than in normal juvenile Shag) pale fringes to the wing coverts and outer scapulars suggest the Mediterranean race of Shag, P. c. desmarestii, and the much brighter yellowish flesh colour to the legs and feet are also a feature of this race. However, similar birds have been observed in Britain and the question of whether they are true desmarestii, or a rare pale morph of nominate aristotelis remains unresolved. Mediterranean Shags often have a strikingly long-looking and slightly thinner bill than nominate, and this is not the case with the Rosslare bird. However, checking a large number of photos of Mediterranean Shag on eBird it is apparent that quite a few do not have bill dimensions that are obviously different to nominate Shag.
This is not the first desmarestii-like juvenile Shag I have seen in Ireland. About 25 years ago I had brief views of a similar bird below the Gannet colony on Great Saltee in summer, but I was on a small boat at the time and did not get a chance to study it in detail.
An interesting paper on the subject by Dave Flumm, published in British Birds in 1993, is available online at the following link:
https://britishbirds.co.uk/wp-content/uploads/article_files/V86/V86_N04/V86_N04_P166_173_A048.pdf
Our Shags are known to exhibit variation in plumage and bare part colouration and it is perhaps more likely that the Rosslare bird is just an extreme example of this, rather than a true desmarestii. Still, it is worth documenting such birds. Curiously, all the British observations have occurred in SW Britain; I am not aware of similar birds having been documented on the Norwegian coast, or elsewhere in northern Europe.
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