Geografische variatie bij Ganzen Deel 2 De oostelijke Grauwe Gans Anser anser rubrirostris

This paper describes the geographical variation within the Eurasian population of the Greylag Goose Anser anser anser, with special attention to the eastern race Anser anser rubrirostris. The watershed between western breeding populations, belonging to the nominate race Anser anser anser (or to a small extent to a North Atlantic type named Anser anser sylvestris) and the eastern breeding race Anser anser rubrirostris is located somewhere in Central Europe and according to several authors (c.f. Glutz von Blotzheim & Bauer, Rutschke, Madsen et al) there should be a broad belt with mixed populations of anser and rubrirostris within this region. However, dealing with personal observations in a large part of the Central European range, the real existence of such a ‘mixed’ population seems to be highly questionable, although definitely an unknown proportion of the regional stock seems to characterized as ‘intergrades’ between the two geographical races. But in this matter intergrading has nothing to do with mixing but is nothing but a natural result of the geographical replacement from one subspecies to another. With respect to the race rubrirostris information is given about the characters on which field observers can recognize this race from the nominate anser, although it seems likely that rubrirostris is a very rare vagrant to Western Europe.