VOOUS KH (1960) 0n the occurrence of East?European Jackdaws Corvus monedula soemmeringii (Fischer) in the Netherlands in the winter 1948 - 1949.. LIMOSA 33 (3): 128-134.

Russian Jackdaw Coloeus monedula soemmerringii East-European Jackdaw Coloeus monedula soemmerringii This is the report on the occurrence of a flock of hundreds of Corvus monedula soemmeringii in the Netherlands (Erp, province Noord-Brabant) during the winter 1948-1949. Through the State Service for Plant Diseases, Wageningen. a series of 56 specimens of this race was collected between January 6 and March 17, 1949. These birds must have had a very limited winter range in the Netherlands. for of a total of 184 Jackdaws collected between January 1 and April 1, 1949, only those collected at Erp and one single adult specimen near Ommen (province Overijssel) (January 25) proved to be distinct from the indigenous race spermologus. Of first-year Jackdaws bred in the Netherlands, by far the majority have left the country in the winter: of a total of 127 specimens of spermologus collected between January 1 and April L 1949. only 6 were in their first year (4.7%). The flock of soemmeringii to the contrary contained large numbers of juveniles, viz. 25 collected specimens (46%). During the period January-March the gonads of the indigenous Netherlands Jackdaws gradually increased in size, indicating the awakening of sexual activity: the average volume of the left testis of 13 adult males in the middle of February being 400 mm3? having increased to 1170 mm3 in the middle of March. In the wintering specimens of the race soemmeringii the gonads remained almost stationary. the average volume of the left testis of 7 adult males in the middle of February being 115 mm3, being still not more than 220 mm3 in the only adult male collected in the middle of March (see table 1). A gradual decrease of the subcutaneous fat deposition was noticed in our own wintering birds from January to March; whereas the fatness of the East European specimens gradually increased in the course of the same period, which was towards the start of the return migration to their East-European breeding grounds. The morphological characters of the Netherlands series of wintering EastEuropean Jackdaws show a rather large individual variation. Notwithstanding this fact, compared with Netherlands spermologus, the light grey underside, light grey hind neck, white patch on the sides of the neck (present in about 84'% of the collected specimens) and the soft and long feathers of upper and under parts proved distinctive in 100': of the specimens collected. The Netherlands specimens of soemmeringii agree very well with the equally variable breeding populations from E. Poland and W. Russia examined in the British Museum (Natural History) and the Natural History Museum at Stockholm (d. Vaous, 1950). Corvus monedula soemmeringii is a well known migratory race of Jackdaw, Several records of its occurrence as autumn passenger and wintering bird in Central Europe have been mentioned in KLEINER'S monograph of this species (1942).

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