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.
[pdf only for members] [dutch summary]