MEININGER PL & BEKHUIS JF (1990) The Mediterranean Gull Larus melanocephalus as a breeding bird in The Netherlands and Europe. LIMOSA 63 (4): 121-134.

Between 1959 and 1970 the Mediterranean Gull Larus melanocephalus was an irregular breeding bird in The Netherlands. Since 1970 it has become a regular breeder and numbers are increasing slowly (89-94 pairs in 1990; tab. I, fig. I and 2). A parallel situation has also been found in neighbouring areas of Belgium (18-19 pairs in 1990). This species breeds mainly in Black-headed Gull colonies. The stronghold of the population is situated in the Delta-area in the southwestern part of the country and the Belgian population in the adjacent area. The Dutch and the Belgian colonies appear to be part of a continuous population and there are movements between them (e.g. increasing numbers in The Netherlands in 1983 and 1986 correspond with decreasing numbers in Belgium). The years 1982-83, 1985 and 1988-90 showed a rather abrupt increase in the Dutch-Belgian population. These three year intervals correspond with the time required for young birds to reach sexual maturity. The abrupt 1989 and 1990 increase in numbers of this species is partly due to a better census technique in some areas; searching for nests gave far better results than just counting the number of adult birds present at anyone time; the latter technique always resulted in a considerable underestimation. In 1989 and 1990 three colonies held ten pairs or more. These breeding pairs clustered in between the nests of Black-headed Gulls. An inquiry made among European ornithologists revealed that the central European population, which was established in the 1950s, showed a slow population growth. A parallel increase in local numbers as found in the Dutch-Belgian population could not be confirmed elsewhere. Almost half ofthe current western and central European population appears to be now found in the Dutch-Belgian Delta area. North of the Mediterranean region Europe holds approximately 175 breeding pairs (excluding USSR). So far this satellite population is characterized by relatively small numbers, distributed over many localities. Since the late 1970s an alternative colonization strategy seems to exist in the European Mediterranean. Here areas are quickly colonized by large numbers of birds occupying a few sites. The Greek population increased markedly, and in Italy two large colonies of Mediterranean Gull were established. It seems that this recent wave of colonization has now reached the Camargue (SFrance). The numbers involved in the Mediterranean population (1988: 8600 pairs) are much larger than in the central European population, although the number of localities is very restricted (fig. 3).

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