KOFFIJBERG K (2006) Identification and moult patterns in first-year Greater White-fronted Geese Anser a. albifrons at the wintering grounds. LIMOSA 79 (4): 163-168.

During age ratio and brood size counts of Greater White-fronted Geese at two important staging areas along the Dutch-German border in 2004/05 and 2005/06, special attention was paid to moult patterns and identification of first-year individuals. First-year birds were identified according to plumage characteristics, behaviour and social interactions. Best characteristics of first-year individuals are the lack (or small size) of the white patch on the forehead, the dark colour of the nail on the bill tip (white in adults), the mottled/scaly plumage pattern on flanks and breast, the lack (or scarcity) of black patches on the belly, rounded instead of edged feathers on back and wing coverts, (often) lack of a white line above the flanks and (sometimes) obvious white tip on the wing coverts (like juvenile Dark-bellied Brent Geese). Four of these characteristics were classified according to fixed criteria (Tab. 1). All observations were made by the same observer, and individuals were systematically selected within flocks of feeding geese. The best characteristics to be used to identify firstyear individuals throughout the season turned out to be dark nail of the bill and the lack of black patches on the belly (Fig. 1). These are retained until March and April and a combination of both allows reliable identification (however, only at close range and not in tall vegetation). The size of the white patch on the forehead (or lack of it in the very beginning of the season) and the scaly plumage on the flanks are useful characters before December, but should only be used in combination with the dark nail and lack of belly patches afterwards. Thus, age-ratio assessments should preferably be made before 1 January, and afterwards only in good conditions at close range and in short vegetation.

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