Geografische variatie en ganzen Deel 7 De Canadese Ganzen Branta canadensis ssp. en Branta hutchinsii ssp

In this article a short description of the geographical variation in Canada Geese (Branta canadensis and Branta hutchinsii) is given. Although all (eleven) actual geographical races of Canada Geese originate from the Nearctic, many of them can actually also be found in Western Europe. This is partly a result of planned introduction (United Kingdom, Fenno-Scandinavia) but also due to birds that have escaped from captivity and to unknown numbers of geese that had spontaneously migrated to Europe and will stay here during winter. Although the breeding population of Western and Northern Europe mainly belongs to the nominate race Branta canadensis canadensis, individuals, pairs or small flocks of almost all the other races can be seen as well, usually together with wintering Western Palearctic geese. It was definitely proven by recoveries of ringed birds that individuals of the smaller type Branta hutchinsii hutchinsii can stay during one winter in the United Kingdom or in Ireland while they were found wintering in earlier or later years in Maryland, USA. So it is very likely that also some birds of the Canada Geese-races seen in Holland during winter belong to the breeding population of Northern America. On the other hand, strongly increasing numbers of Canada Geese mainly of the nominate race canadensis, are breeding throughout The Netherlands which resulted in an actual stock that has already reached a level of at least 1900-2200 breeding pairs and about 7500-9000 wintering birds.