ROOTH J & BRUINS MFM (1959) The Sandwich Tern Sterna sandvicensis sandvicensis as a breeding-bird in the Netherlands. LIMOSA 32 (1): 13-22.

The breeding population of Sandwich Tern (Sterna s. sandvicensis Lath.) in the Netherlands fluctuated in the period 1954-1957 between 25000 and 40000 breeding pairs. This is about 415 of the total N.W. European breeding population. The Terns breed in 7 greater colonies, where they nest every year. These breeding-places are situated along the Northsea-coast (i.e. Rottumeroog, Griend, Texel, Makkumerwaard, de Beer, de Scheelhoek en Schouwen, see map). The numbers of breeding pairs per colony are given. Six other breeding sites are known, where the Sandwich Tern started breeding in recent years. These colonies are sometimes very small. It is not possible to foretell whether these colonies will maintain themselves in the future or not: Schiermonnikoog, Den Helder, Veluwemeer, Hompelvoet, Zandkreek, Rammekenshoek. Nine localities are known where Sandwich Tern-colonies and occasionally even great ones, established themselves temporarily for a single or a couple of years The numbers of breeding pairs fluctuate greatly per colony. A certain interaction between neighbouring colonies could be found. The total number of breeding pairs in the Netherlands therefore is more constant than are the numbers in each colony. The fluctiations however are great. Occasionally high mortality among nestlings, due to bad weather conditions will probably be the reason for this. This happens when in the period shortly after hatching the weather is bad for a relatively long time with strong winds and low temperatures. The adult birds cannot find enough food then and the chicks die from hunger and cold. Influence from the Blackheaded Gull (Lams ridibundus) which often breeds near or in the Tern-colonies is not as bad as is sometimes supposed. The Gulls predate to a certain extent on eggs and young, but the loss is of no great importance. On the other hand the Terns profit by the presence of the stronger and more aggressive Gulls. Three of the seven greater permanent Sandwich Tern-colonies are threatened with extinction (by natural erosion, establishment of industry and by the Deltaworks). It is therefore desirable to give the other colonies the status of reserve, which guarantees their existence ##### Sandwich Tern Thalasseus sandvicensis = Sterna sandvicensis

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