Saturday, 9 July 2011

Audouin's Gull

A few pairs of Audouin’s Gulls have been breeding in the Algarve since 2001 and the species can be seen here throughout the year. They are mainly nocturnal feeders, spending their days loafing on the saltpans and, as they often stay faithful to the same areas for weeks or even months, they’re easily found.

The world population of Audouin’s Gulls is now something like 21,500 pairs, a remarkable total bearing in mind that as recently as 1975 there were thought to be only 1,000 pairs.

The increase in numbers is the result of the establishment in 1981 of an extremely successful breeding colony at La Punta de la Banya in the Ebro Delta in Spain. This colony, which has been extensively studied, now holds roughly 65% of the world total. As well as in Spain and in Portugal, there are breeding colonies in Algeria, Croatia, Cyprus, Greece, Corsica (France), Italy, Morocco, Turkey and Tunisia.

Although most Audouin’s Gulls spend the winter around the southern Mediterranean, many, particularly young birds, find their way down the coast of West Africa to Mauritania, Gambia, Senegal and Gabon.

The initial success of the Ebro Delta colony was said to result from a ready supply of food in the form of discards from the local fishing industry. A trawler moratorium from 1991 to 2000 that coincided with the birds’ breeding season put an end to this easy life for the gulls but it had little effect on the colony’s growth as they sought alternative food sources and ranged more widely along the coast. The introduced American Red Swamp Crayfish, abundant in the area’s extensive rice fields, became an important food source. When fishing recommenced the renewed availability of fish waste naturally gave a substantial boost to the population.

With such a high percentage of the population concentrated at one site and dependent to quite a high degree on a trawling fishery that is considered unsustainable, Audouin’s Gull is classified as ‘Near Threatened’ on the IUCN Red List.

In the last five years we have reported details of about 40 darvic-ringed birds that we have seen around Tavira and Santa Luzia. Replies with ringing details and life histories are very slow to arrive but so far, not surprisingly, all have been from the Ebro Delta or satellite colonies nearby, including one from Isla Moltona, Mallorca. In the last few days we have been seeing a bird that we first reported two years ago and which was ringed as a pullus in 2002.

Jean Victoire Audouin (1797-1841), for whom the species is named, was a French naturalist, an entomologist, ornithologist and malacologist.

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