COTTAAR F (2019) Pink-footed Geese Anser brachyrhynchus preferred harvested maize over grass as a food resource in Friesland in autumn 2017. LIMOSA 92 (1): 24-27.

The southwestern lake district of the province of Friesland used to be a main staging area for Pink-footed Geese of the Svalbard breeding population, but numbers have significantly declined over the last ten years, as more and more geese prefer to stay further north in the flyway, in Denmark. In the autumn of 2017 the geese arrived rather late in Friesland (mid October instead of late September), and in small numbers (4000-4500). The seasonal maximum in December was about one month later compared to previous years, and again lower than in previous years. Moreover, the goose flocks showed a remarkable distribution as all of them were found on harvested maize fields. In search of harvested maize fields, flocks of geese also moved to other areas, outside their traditional range in the lake district, e.g. to areas in the far southeast of the province, where maize occurs on a much wider scale. Exploitation of harvested maize fields by Pink-footed Geese has been increasingly observed elsewhere along the flyway, and is regarded as a major driver for the observed changes in migration strategy in the species. Detailed studies have shown its superior food quality. However, in Southwest-Friesland, flocks so far mainly relied on improved pastures for feeding. Why the Pink-footed Geese switched to harvested maize in Friesland in the autumn of 2017 is not clear. Apart from the learning effect elsewhere in the flyway, the timing of arrival in relation to harvest of maize may have been more optimal in 2017, or the energy content of maize even more superior due to the long growing season of grass as a result of high autumn temperatures. The autumn of 2017 may have initiated Pink-footed Geese to change their feeding preferences in Friesland and move away from their traditional staging areas in grassland polders, as has been observed elsewhere along the flyway.

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