Status en veldkenmerken van Pontische Meeuw Larus cachinnans en Geelpootmeeuw Larus michahellis
Spanoghe, G. (2002). Status en veldkenmerken van Pontische Meeuw Larus cachinnans en Geelpootmeeuw Larus michahellis, in: Natuur.oriolus. Themanummer Meeuwen. Natuur.Oriolus, 68(3): pp. 158-171
In: (2002). Natuur.oriolus. Themanummer Meeuwen. Natuur.Oriolus, 68(3)[s.n.][s.l.], more
In: Natuur.Oriolus. Natuurpunt Antwerpen Noord: Turnhout. ISSN 1379-8863, more
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| Keywords |
Identification keys
Population characteristics
Larus cachinnans Pallas, 1811 [WoRMS]; Larus michahellis J.F. Naumann, 1840 [WoRMS]
ANE, Belgium, Belgian Coast [Marine Regions]
Marine/Coastal |
| Abstract |
Recent knowledge on large gulls increased from work by professional as well as amateur ornithologists. One of the most striking results was the discovery that the Yellow-legged Gulls could be identified on subspecies level and more importantly that nominate cachinnans occurs regularly in Western Europe. Morphological, ecological and fylogenetical research indicate, contrary to current classification, that this taxon should be treated as a full species: the Caspian Gull Larus cachinnans which breeds in large numbers in the Black and the Caspian Sea area. The Yellow-legged Gull should consequently be named Larus michahellis. This taxon has its main range around the Mediterranean. Both species occur in Belgium with annually several hundreds of Yellowlegged Gulls (mainly late summer) and several tens of Caspian Gulls (mainly winter). Adult and immature plumages differ between both species and especially from Herring and Lesser Black-backed Gulls. Structure, call and behaviour are additional differences. Due to a broad variation in almost every identification feature, it should be stressed that even the most experienced gull-watcher isn’t able to identify every gull he encounters. Structurally Caspian Gull has a long and slender body (with a high breast), a usually long, parallel shaped bill without a clear gonysangle, a sloping forehead and strikingly long, thin legs. Yellow-legged Gull is more heavily built with a more squarish head, a deeper breast and has an on average heavier bill with a clearer gonysangle than even Herring Gull. Adult birds show an important difference in wingtip pattern: both Yellow-legged and Caspian Gull show extensive black on six primaries (usually 5 in Herring Gull), the black is however reduced in Caspian Gull by long greyish/whitish tongues on the inner web of the longest primaries. This pattern is reminiscent of Scandinavian Herring Gulls. Caspian Gulls have an on average darker eye, a paler back and less brightly coloured yellow legs and bill than Yellow-legged Gull. First calendar-year Caspian Gulls show the following differences with Yellow-legged Gulls: a pale wing-bar across the greater coverts, dark tertials with light edges, a paler window in the primaries, a paler underwing, a paler bill, even whiter underparts and a finer pattern of the new first-winter scapulars. Especially Yellowlegged Gull, but to a lesser extent also Caspian Gulls, can show several new moulted wing coverts and tertials by the autumn, a character never shown by Herring Gull. The subsequent immature plumages are more difficult to identify which leaves structure as one of the most important distinguishing features.Moult can be an important indication in identifying, rarely a discriminating feature: Yellow-legged Gull moults on average one month earlier than Herring Gull, Caspian Gull falls in between. Caspian Gulls have a very different call from both Yellow-legged and Herring Gull. They frequently raise there head vertically with opened wings during calling (long call) which creates the fairly typical albatros-posture. |
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