Geografische variatie bij ganzen Deel 9 De Zwarte Rotgans Branta (bernicla) nigricans

In The Netherlands, the Black Brent is a scarce bird, which was first recognized on the island of Terschelling in november 1974. Afterwards it became a regular winter visitor to the coastal regions, usually seen together with flocks of Black-bellied Brents of the nominate race bernicla. During the period 1980-‘98 a total number of 72 observations, containing 97 individuals, was reported, but a slight increase was observed from 1998 onwards until the present. So, in the season 2001-‘02 at least 53 birds were reported, but as some of the observations could be dealing with the same birds, it is not clear how many Black Brents really were visiting the country by then. The first type description of ‘ Anser nigricans’ originates from 1846, as Lawrence was describing three geese which were collected at New Jersey along the Atlantic coast of North America and they got the name Lawrence’ Brant Goose. It is probable that these birds belonged to a small breeding population of the Northern Hudson Bay region, which was almost extinct by the late 40’s of the 20th century. Meanwhile, the name nigricans was also used for Brent Geese which were breeding in Eastern Siberia and Northwest America. These geese are wintering along the coasts of the Pacific as well as along the Asiatic mainland and adjacent islands to Japan as along the American West coast from Vancouver Island south to Lower California. The first author who switched the name nigricans over to birds of this type already was Coues (1872-‘74) and afterwards also Taczanowski (1893), Rheichenow (1882), Seebohm (1884) and Alpheraky (1904) were using this name with respect to breeding birds of Eastern Siberia and Northwestern America. However, the new name Branta bernicla orientalis was given to Brent Geese of these regions by Tougarinov (1941) and was used during several decades but, once again, at the present almost every author is using the name nigricans with respect to these birds. Anyway, the actual size of the population of Lawrence’ Brent (i. c. the original nigricans) seems to be unknown and maybe it has already disappeared completely. On the other hand, the population of Eastern Siberia and Northwest America can be split in an Asiatic wintering population of about 7000 birds and a population that winters along the western coast of the North American mainland. The actual size of this population should be about 130,000 individuals. According to recent changes in the systematics of the Dutch Avifaunal List all races of Brent Geese are conceived as species by means of their separated distribution within the breeding ranges. However, recently several mixed colonies of Black-bellied Brent and Black Brent were found in the Olenyok Delta and Lena Delta in the very north of Central Siberia. So the Dutch decision to classify both types as separated species will be questionable.