Geografische variatie bij ganzen Deel 4 De Oost-Siberische Taigagans of Middendorff’s Gans Anser fabalis middendorffii

In this contribution a description of the eastern Taiga-breeding race Anser fabalis middendorffii is given. Middendorffii breeds in mountain-forest habitats throughout Central and Eastern Siberia, roughly from the eastern Yenisse region to the Kamchatka peninsula. The northern and eastern boundaries of the breeding range are yet still uncertain, but according to Delacour (1954) it probably can breed as far south as the southern Altay and northern Mongolia. The regular winterquarters of middendorffii are situated in Japan, North and South Korea and in China. It is uncertain to what extent the race is wintering elsewhere in Asia, but probably small numbers will occur as far southwest as the Black Sea region. Although the size of the entire world population of middendorffii was estimated by Fox (1996) as to be less than 10,000 birds, this definitely was a far too low number as moulting flocks on the Kamchatka peninsula numbered up to 8,000-10,000 birds during the late nineties. So, in my opinion, it is not unlikely that the actual size of the population of middendorffii will be at least twice as high as the number estimated by Fox. In the Netherlands the race was first seen on January 18th 1982, when a juvenile bird showed up in a flock of 840 A. f fabalis and 440 A. s. rossicus near Maurik, province of Gelderland. In January 1985 one bird was shot out of a flock of five birds near Engelen, province of North Brabant. From the 1995-‘96 season until the present families as well as small flocks of middendorffii are observed every winter in the Netherlands so that it seems clear that middendorffii has become a regular winter visitor in very small numbers. Most observations are located in the eastern parts of the country and these birds merely were feeding in marshy pastures of the ‘old-fashioned’ type. Middendorff’s Geese recently were also observed in several geese-haunts in Central Europe. It is not clear whether these birds really has switched over from Asiatic haunts to Europe during the latter part of the nineties or if the birds now seen in The Netherlands formerly were wintering in some unknown haunts somewhere in Eastern Europe. If the latter will be the case, it is not unlikely that the birds have wintered (or are still wintering) in the Black Sea region and especially in the Danube Delta.