1.Ökologische Analyse von Auestandorten anhand der Fauna und Flora
[The factors limiting breeding success in the Black-headed Gull Larus ridibundus in different habitat types on the middle course of the Vistula River, Poland]
Bukaciński, Dariusz; Bukacińska, Monika
The Black-headed Gull (Larus ridibundus) on the Vistula River islands selects its breeding habitat irrespectively of water level. Grassy areas are chosen first of all, bare sands - the latest. The breeding success is not related only to the quality of habitat. Egg mortality is related to the level of water and habitat characteristics. Only in the years of medium water level the breeding success is the highest in grassy areas (predation being the main cause of losses). In the years of high water level flooding equally limits the breeding success in all habitats. Whereas in the years of low water, when pasturage of cattle and sheep is the main mortality factor, the highest breeding success is found on bare sands. Summing up, in such fluctuating environments as the islands of unregulated rivers, the variety of different habitats guarantees the highest breeding success in dependence of time (over the years) and fluctuating water levels.