IMPE J VAN (1973) Age group ratio counts of Bean Geese in the field. LIMOSA 46 (3): 192-198.

Taiga Bean Goose Anser fabalis During three consecutive winter seasons, studies were made of plumage differences, proportion of young birds and family groups in Bean Geese, wintering in the polders of the province of Zeeland. There is some doubt whether these Bean Geese belong to a mixed population A.f. fabalis ;: rossicus with mainly characters of rossicus or to the true subspecies A.f. rossicus. The distinction between juvenile birds and others is not easy for the field observer owing to paucity of information in the literature and the close resemblance between the plumages of the two classes. This is the reason why excellent conditions of observation are very important. The colour of the legs and the white feathers at the base of the bill are not apt to distinguish the two classes. The former are variable in birds in adult plumage and the latter are regularly absent in adults, while in juveniles they may rarely be present. A rufous tinge on head- and neckfeathers, which according to the literature is characteristic for juveniles, was never observed. Adults show in most instances the obvious white sidebar and on the great and median wingcoverts, the white tips form distinct, transversal bars. On the sides of the body and the flanks? bright and dark transversal streaks are visible. All these field characters may become VIsible in juveniles. by an early moult and in late winter. Then their use is of less value as field character for adults. Juveniles sometimes present dark markings on the sides of the breast and belly; a bright colour of the breast and/or belly may also be present in these birds. The colour of the bill is brighter in juveniles than in adults. There are howe'ver exceptions and a good identification will only be possible when all the field characters are taken into account. Table I gives the proportion of geese in first-year plumage. It seems that the summer 1971 was characterised by lower breeding results than those of the two preceding summers. Winter counts in Zeeland indicated also low breeding results of Whitefronted, Barnacle and Brent Geese in 1971. The recognition of family groups is very difficult in the field, because many birds are walking or feeding without any family connection. Some results are presented in Table 2. The mean brood size for 33 families was 2,06. The value of this number in Bean Geese is further discussed.

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