Hivernada de Làrids "(Aves: Laridae)" al litoral del Principat i del País Valencià (1980 i 1981)

Resum

The results of two winter censuses of gulls, performed on the Spanish Mediterranean coast, in the provinces of Girona, Barcelona, Tarragona, Castelló and Valencià in 1980 and 1981, are given
 The results obtained were:
Species 1980 1981 Estimated minimum Larus fuscus 5,401 4,807 6,000 Larus argentatus 27,616 21,591 30,000 Larus melanocephalus 15,593 12,571 18,000 Larus minutus 501,000 852,000 1,000 Larus ridibundus 59,321 54,961 75,000 Total: 108,432 94,781 130,000  
The main concentrations of gulls were observed in Roses bay (\simeq 15,000 individuals), Medes Islands (\simeq 15-17,000), Barcelona-Llobregat Delta (\simeq 8-9,000), L'Ametlla-Ebre Delta (\simeq 22,00), Vinaròs-Castelló (\simeq 20,000), Albufera and surroundings (\simeq 15,000).
The most important novelties observed between this and another census realized in the same area in the 1977 and 1979 winters (CARRERA et al., 1981a), are:
Larus fuscus: A remarkable increase in the censed figure, due to a better census of the Castelló province fishing harbours (Benicarló-Grau), where the 50 % of the total censed on the coast was found.
Larus argentatus: An increase of the censed figure due to a better counting of the Medes Islands sleeping place and other littoral coast points. By checking the ratio adults/ subadults-immatures by province, we find that the percentage becomes more equal as we move farther from the principal reproduction centres (province of Girona).
Two new winter recoveries of birds born in the Medes Islands, one in the Camargue and the other in Castelló, are commented.
Larus melanocephalus: An increase of the censed figure due to a better census of the fishing harbours of the province of Castelló, that had been subestimated in previous census.
Larus minutus: The concentration of about 1,000 individuals at the Llobregat Delta is mantained. Sporadic observations in other places of Catalonia are performed.
Larus ridibundus: The main reasons for the traditional low estimation of this species are commented. A minimum estimated figure per province is given.
No observation of Rissa tridactyla, Larus canus, Larus marinus, Larus adouinii, is performed.