De Zwartkopmeeuw Larus melanocephalus in de duinen van Schoorl (NH)

This paper deals with the occurrence of breeding Mediterranean Gulls in the mixed gull colony in the dunes of Schoort (Noord-Holland), from 1972 onwards. Each year 1-4 pairs were present, always consisting of two apparently adult birds (table 1). Second summer individuals were observed regularly as well, but they were never paired (table 2). The nesting attempts invariably occurred among the established Common Gull nests, but were seldom successful, because of the extreme vulnerability for disturbance. The Mediterranean Gulls flew off at the slightest interference by any other gull, staying away for hours on end and often returning separately. Thus, their nests were very much exposed to predation by Foxes, or by the larger gull species present nearby. Their favourite feeding haunt was found in the nearby Noorder-Rekerpolder (cf. figure 1), a moist grassland area. Rather frequently they were observed as well during seawatches at the nearby Hondsbossche Zeewering (table 4). It is argued, that the establishment of Mediterranean Gulls in Schoorl may have taken place before 1972, but it seems unlikely that they arrived before the sixties. Finally, it is assumed that, in spite of the apparent attraction of this area for Mediterranean Gulls, any stable and sound breeding population of this species within the Schoorl gull colony will only take place, if various pairs would settle closer together to fence off disturbance by Common Gulls and thus achieve a higher reproductive output.