The aim of this study is to study individual usage patterns of wintering grounds by Greylag Geese to get an insight into how individual patterns may influence the overall pictures obtained from counts and similar surveyes. Questions I want to find and answer to are: 1) How geese from different breeding areas are distributed in the wintering areas, especially if geese from different breeding areas form recognizable subflocks (i.e. if they use different localities) or if mixed flocks are formed. 2) If geese arriving later in autumn occupy less profitable habitats. 3) If geese using marginal habitats have a worse body condition.

Specifically I'm going to study:
- When geese from different breeding areas arrive to the marismas.
- To which parts of the Marismas the geese arrive.
- If the geese change between different parts of the Marismas during winter.
- What habitats the goose uses.
- The body condition (abdominal profile index; cf. Owen 1981) of the geese when they arrive.
- How the body condition changes during the winter.