VLEUGEL DA (1960) Observations on the Spread of the Black Redstart Phoenicurus ochruros in the Netherlands. LIMOSA 33 (1): 6-18.

1. A number of observers collected information on the extension of the Black Redstart from 1942 - 1950. The material is scanty, because the spread of the Black Redstart apparently proceeds only slowly and is not great over a period of eight years. Information on the bird's spread over the same period in England, collected chiefly by R. S. R. FITTER, was obtained from the literature. Some data for the period 1920-1942 were also considered. The numbers in England and The Netherlands (Table 1) cannot be compared without explanation. Those for The Netherlands which relate to the extension in the west and north where the Black Redstart is rare or absent, only refer to places where the species only occurred once or twice. They consequently give roughly the increase in the respective years. The places where the Black Redstart breeds more or less regularly, have been left out. The English data, on the other hand, are the absolute numbers of Black Redstarts which have been observed in the respective years. 2. As regards the period 1942-1950, the years with most Black Redstarts were 1942, 1943, 1949 and 1950, both in The Netherlands and in Great Britain. 1948 was only a peak year in England. The reason seems to be that the breeding Redstarts at The Hague in 1948 had not yet been discovered, but probably did occur there already as they did in 1949. The following circumstances appear to be favourable for the spread of the Black Redstart: a. A good breeding-season in the previous summer as egards temperature and hours of sunshine. b. Tempe'rature and hours of sunshine above normal in the migration period (especially second decade of March). c. When there were more favourable i.e. eastern and south eastern w;nds in the migration period than normal. d. When there were fewer unfavourable i.e. western and north western winds than normal in the migration period. However, this is not so clearly shown as the circumstances mentioned under c. 3. Other good years for the spread of the Black Redstart in England were 1923, 1933 and 1941. Information for The Netherlands before 1941 is very scarce, but 1941 was also a good year. In the main the same favourable ircumstances as mentioned under 2 were found, at least according to the Netherlands Meteorological Institute at De Bilt near Utrecht. 4. There seemed to be a certain persistence in the colonization as was also found in England. Some places were visited for years at a stretch, other places have been regular breeding-places in nearly all or all years. 5. There was always a number of unmated males which seem to be the vanguard of colonization. 6. There were two colonies of several pairs in towns with war damage: a. Rotterdam 1943-1945. b. The Hague 1949-1950. In both places the colonies disapppc:red when the respective parts of these towns had been rebuilt. Black Redstart Phoenicurus ochruros

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