IJZENDOORN ALJV (1950) The breeding birds 0f the Wieringermeerpolder in 1948 and 1949. LIMOSA 23 (3): 338-357.

The Wieringermeerpolder. an area reclaimed from the Zuiderzee in 1930. was again studied in order to find out whether any changes had taken place in the build-up of the breeding birds' population. Lack of time prevented such an intensive research as was made in previous. years (VAN IJZENDOORN. '1947 and 1948). Comparison with the data available from 1945. 1946 and 1947 reveals that it is especially the "reed-birds" that showed an increase in numbers. Acrocephalus scirpaceus, Emberiza schoeniclus, Acrocephalus schoenobaenus nested in the polder in somewhat greater numbers than in previous years. Gallinula chloropus, perhaps also Anas platyrhynchos and Anas querquedula. also took advantage of the gradual recovery of the reed (Phragmites communis) along the borders of most canals. It is expected that this increase will go on in the coming few years.
      The Bearded Tit (Panurus biarmicus) nested in the reeds that have grown up to a considerable height near the "Dijkgat": the place where the dyke was blown up by the German army in April 1945 in order to flood this fertile polder. The scarcity of mice (especially Microtus arpalis) was presumably the cause of the non-breeding of Asio flammeus and the few nests of Asio otus and Falco tinnunculus.
      least one territory of Acrocephalus schoenobaenus and Emberiza schoeniclus. Undoubtedly aberrant habitats for these three species! Acrocephalus arundinaceus was in 1948 only observed in the marginal canals of the polder. In 1949, however, there was 1 territory in the reeds of a canal in the polder. So it is presumed that the reeds are still for the greater part too low and not dense enough to allow this species to breed in the polder. Turdus merula is also a rare breeding bird, the cause of which is not quite understood.
      Riparia riparia nested in two colonies (at least 15 pairs). Wholesale destruction of eggs and nests was due to human agencies, Recurvirostra avosetta liked to nest on sandy fields planted with sugarbeets or potatoes, lying close to shallow canals, where young ones stay till they can fly. Near the "Dijkgat" there were again colonies of Sterna hirundo, Recurvirostra avosetta, Charadrius hiaticula and Leucopolius alexandrinus. Sterna minuta had disappeared in 1949 as had Larus ridibundus, This latter species still was a breeder here in 1948, whereas in 1949 a small colony had settled in "Robbenoord". The landscape near the "Dijkgat" is gradually getting more overgrown and the colonies of waders, terns and gulls will presumably disappear completely in future years.

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