| Title |
Caspian Gull Larus cachinnans in France : status and identification |
|
| Author |
Philippe J. Dubois |
| Language |
French |
| Magazine |
Ornithos, vol. 13, no. 6, 2006
|
| Page |
336 - 367 |
Contents
|
Original title in French: Le Goéland pontique [Larus cachinnans] en France : statut et éléments d’identification
Summary in English:
Since the first field record in February 1997, the Caspian Gull is now a rare but regular winter visitor in France. From the 198 collected records up to April 2005 (about 243 birds), it appears that most of the birds are seen in northern France (Nord-Pas-de-Calais), the Île-de-France (Paris region), and eastern France (Alsace), totalling 79 % of all the records. Elsewhere, the species is either rare, but regular, (River Loire, Mediterranean seashore) or accidental.
There are about 40 birds per winter, but this is probably an underestimate and the true number may be around 100 birds. The age-ratio shows that 63% of identified birds are adults (or 4th calendar-year), 9% are 3rd cy, 18% are 2nd cy and 11% are 1st cy. The latter are probably underestimated and are likely to be overlooked in groups of large gulls.
In autumn, the main arrival of Caspian Gulls occurs from mid-November to early December. Birds depart from mid-February up to the end of March. Some lingering birds are seen later, and a few birds probably summer in Northern France.
It is interesting to note that there are small differences in the dates of arrival of birds between northern France (beginning of December), the Paris region (December and January) and Alsace (mid-December to the end of January). So, a possible conclusion is : birds arrive from the Baltic and the North Sea, after coming from eastern Europe, by following the large rivers. Then they shift up to northern France (so they arrive later in the season) and by mid-winter they start to return towards their breeding area using again the ''river flyway'' and taking the shortest route (via eastern France). The migration route could possibly be a loop like some other eastern species.
There are 4 controls of ringed birds in France coming from Ukraine, Poland and Germany.
The second part of this paper deals with the identification of the species (using the calendar-year scale). Apart from the classical (better known) features, it emphasises potential pitfalls with other species, particularly Yellow-legged and Herring Gulls (both [argenteus] and [argentatus], including ''yellow-legged'' birds), since it appears that some birds are still misidentified in the field. In particular the adult Herring Gull in late winter (with full summer plumage), and especially the ''yellow-legged'' form from the Baltic area, is a real pitfall with adult Caspian Gull in ''summer'' plumage. It contributes probably to overestimates of this age class in France. For younger birds, some 2nd cy Yellow-legged Gulls are particularly tricky. Some birds are almost identical to Caspian Gulls of the same age. Structure can be a help for a correct identification. The same is true for older birds and some 4th cy Yellow-legged Gulls with a very late moult phase are very similar to younger Caspian Gulls.
Since some Yellow-legged or Herring Gulls can hybridize with Caspian Gull (particularly in Poland) some hybrids can reach western Europe and complicate the problem further.
|
| |
Contents of this issue:
|
|
|
» View trip reports, checklists, forum etc. about birding in France on Travellingbirder.com
|
