SCHARRINGA CJG & MIRANDA JF DE (1977) The occurrence and the status of the White-winged Black Tern Chlidonias leucopterus in The Netherlands. LIMOSA 50 (1): 27-33.

White-winged Tern Chlidonias leucopterus Although the White-winged Black Tern, Chlidonias leudopterus, was considered to be a straggler (Avifauna van Nederland 1970), at present the status in the Netherlands is that of an irregular visitor. Up to and including 1971 immature birds have not been recorded in the Netherlands, although since many years immature birds are the greater part of autumn Whitewinged Black Terns in Great Britain. This contrast and the increasing number of records were a reason to analyse the occurrence in the Netherlands and to compare the data with the picture from Great Britain. The annual pattern of White-winged Black Terns in the Netherlands and the annual pattern of adult and immature birds during 1958-1975 are shown in Table I and Table 2. The seasonal patterns of the records are shown in Figure I and Figure 2. Comparing the Dutch records with the data from Great Britain, a great contrast is found in the ratio adult/immature in the autumn records. This is most striking in the records from 1958-1971 when in the Netherlands only adult White-winged Black Terns were recorded. As all immature birds recorded during 1972-1975 were observed by a few observers only, it looks obvious that immature birds were not recognised in the years before 1972. This and the fact that the species was recorded every year during 1968-1975 is a reason why the authors propose to change the status in that of a migrant.

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