RapportHabitat selection by the Corncrake

Habitat selection by the Corncrake
Omslag Habitat selection by the Corncrake

Distribution of Corncrake Crex crex in the floodplains of the Dutch Rhine branches was studied. Data
on male singing sites from the period 2001-2005 were used. Occurrences and numbers of singing sites
were related to ecotopes and inundation frequency. Landscape characteristics of floodplains with
different occupation frequencies were compared.
The ecotopes "production meadows" (41%) and "pastures" (28%) are preferred habitat for the
Corncrake. Reference densities for the most important ecotopes varied from 0.1 to 0.62 singing males /
ha. Results proof that a shift in ecotope preference occurs when the season proceeds: production
meadows become less favourable and natural pastures and herbaceous grasslands more. This is
probably caused by mowing activities in the middle of June.
There were no significant differences in amount of suitable habitat between floodplains that were
occupied in one, two, three or more of the years. Floodplains with a higher occupation frequency show
a higher Shannon Index score. Also, these floodplains contain less different patch types. This suggests
a preference of the Corncrake for heterogenic landscapes with a limited number of different ecotopes
that are represented equally in the area. However, based on these results it can not be concluded that
habitat availability is a key factor in settlement of the Corncrake in the floodplains. Probably other
factors like land use are of more importance.

Radboud University Nijmegen/SOVON Vogelonderzoek Nederland, Nijmegen/Beek-Ubbergen
Report Environmental Science nr 294/2006/09