Ardea
Official journal of the Netherlands Ornithologists' Union

login


[close window] [previous abstract] [next abstract]

Kist J. (1956) Het voorkomen van de rassen van de Rietgans, Anser fabalis, in Nederland. ARDEA 44 (1-3): 188-206
On the basis of Delacour's (1951, 1954) subdivision of the Bean Goose, Anser fabalis (Latham), into 6 subspecies it is shown that 5 of them occur or have, occurred in Holland. 1. Owing to the fact that the European Bean Goose, Anser fabalis fabalis, for a long time has been confused with rossicus (the segetum-type of Bean Goose of Naumann and Alpheraky), the quantitative status of this subspecies in Holland is not exactly known. Nevertheless, recent field work makes it very probable, that fabalis is our commonest Bean Goose which in many thousands winter in Holland. Under favourable circumstances fabalis can be identified in the field with reasonable certainty. Compared with rossicus it is a rather large goose of elongate shape of body with a long neck and with a fairly long and slender bill which as a rule is more yellow than black and has a straight lower mandible. 2. Johansen's Bean Goose, Anser fabalis johanseni, recently described by Delacour (1951) as a clinal intermediate form between fabalis and the east-Siberian race middendorfi, has not yet been officially admitted to the Dutch list. However, it is clear that the two specimina, mentioned by Voous (1944) as belonging to an eastern population of fabalis [? Nov. 1938; wing 505 mm; culmen 64 mm] c.q. to a transitional form between fabalis and sibiricus (Alpheraky) [? 7-12-1927; wing 430 mm; culmen 67 mm], must be recognised as belonging to this newly discovered west-Siberian race johanseni. With fabalis Johanseni belongs to the group of Taiga Bean Geese, but in all its mean measurements it is a larger bird. If Delacour is right in stating that johanseni as a rule has' a black bill with only a sub apical orange-yellow ring before the nares, it must be possible to identify this subspecies in the field with a fair degree of certainty. Last winter the author saw a small flock of large Bean Geese all of which showed a straight and slender black bill with only a yellow ring behind the nail and he would not be surprised if it came out that johanseni must be 204 [Ardea 44 regarded as a more or less irregular winter visitor to the Netherlands. 3. On December 19th, 1946, a juvenile bird of the year was caught near Barneveld (wing 438 mm; culmen 63,8 mm; greatest depth of lower mandible between 10 and 11 mm) which Voous (1948) considered to belong to the east-Siberian tundra form Anser fabalis serrirostris, Thick-billed Bean Goose. However, as Delacour gives a minimum length of culmen of 65 mm for serrirostris and a maximum of 66 mm for rossicus, no serious objections could be made if one would refer this specimen to an eastern population of rossicus or to the zone of intergradations between these two forms near the mouth of the Khatanga River. 4. The Russian Bean Goose (which is a misleading name), Anser fabalis rossicus, is .the west-siberian form of the Tundra Bean Goose group, which only recently has been established as occurring more or less regularly in Holland. Voous (1944) discovered in the Zoological Museum of Amsterdam a specimen (January 18th, 1888) which he identified as rossicus and claimed it as a new subspecies to the avifaunal list of Holland and Europe outside Russia. Coombes showed that Voous was mistaken concerning the status of this form and in thinking that it differs in any way from the segetum-type of Bean Goose which Voous thought to be an ecological race within the subspecies A. f. fabalis. In Dutch and British collections Coombes found 28 skins of rossicus all of which were shot in the Netherlands between 1896 and 1947. Furthermore, Coombes stated that according to his considerable experience as a goose hunter and -watcher the provinces of South Holland and Zeeland are the regular winter quarters of large flocks of Bean Geese most if not all of which belong to the tundra form rossicus. Recent field observations have revealed the fact that rossicus does occur in Zeeland and South Holland. However, it was proved also that fabalis is very much more the commonest and most numerous winter visitor to these provinces. Under favourable circumstances rossicus can be distinguished in the field from fabalis. Rossicus is a rather small and stocky goose with a short, thick and curved bill which is black with a narrow orange-yellow sub apical ring. The writer observed last winter a flock of about 100 rossicus the majority of which (the immature birds) showed only a yellow spot on the upper mandible. This observation is in full accordance with the description which Naumann gave of birds of the year of his Anser segetum. 5. The Pink-footed Goose, Anser fabalis bracryrhynchus, is a scarce winter visitor to Holland and definitely less numerous than all other geese which winter regularly in this country. Though there is no final proof that this geographically isolated form has reached the threshold of reproductive isolation, the writer (who is not a competent taxonomist) nevertheless is of the opinion that bracryrrynchus which differs clearly from the other Bean Geese not only in morphological characters but also in ecological and ethological aspects, should be regarded as a separate species. 6. Summarizing the writer points out that identifying the Bean Goose (except the Pink-footed Goose) sub specifically in the field 'S far from an easy task and that only experienced field-observers may come to reliable conclusions if the observation is made under favourable circumstances. Moreover, it must not be overlooked that the geographical variation in both groups of tundra and taiga-geese is of a clinal character and that in the border zones of their breeding grounds the subspecies interbreeds and intergrades freely with each other. The whole wooded tundra of arctic European Russia is inhabited by a mixed population fabalis-rossicus. It is therefore probable that Bean Geese of intermediate and mixed characters visit Western Europe. To prevent unwarranted conclusions subspecifical field-identification should as a rule be affected by examining the whole flock by families, not one by one. 7. In a postscript the writer refers to his correspondence with Voous, who now is of the opinion that Naumann's 'Saatgans' (Anser segetum) represents the very variable mixed population of taiga- and tundra-geese which inhabits Northern Russia and that Coombes designated this population as rossicus, whereas Voous himself uses this name only for the 'true' tundra-geese breeding in the west-siberian tundra. The writer points out that Voous is mistaken in thinking that Naumann's segetum is something else than the 'true' tundra-goose of the west-Siberian peninsulas. Naumann's 'Saatgans' was definitely not a variable goose, but on the contrary a very strict form which in all its measurements (incl. shape and colour of the bill) fully conforms to the most western populations of the siberian race rossicus as described by Delacour. On the other hand, the writer agrees with Voous that it is not improbable that Coombes starts from a much wider conception of rossicus. This would explain why Coombes saw so many tundra-geese in Holland.


[close window] [previous abstract] [next abstract]