Do Reeves make different choices? Meadow selection by spring staging Ruffs Philomachus pugnax in Southwest Friesland Each spring Ruffs stop over in large numbers in the northern part of the Netherlands, especially in Southwest Friesland....
moreDo Reeves make different choices? Meadow selection by spring staging Ruffs Philomachus pugnax in Southwest Friesland
Each spring Ruffs stop over in large numbers in the northern part of the Netherlands, especially in Southwest Friesland. While staging, Ruffs use meadows for feeding and refuelling. A general believe is that they are attracted by the typical Dutch wet peat grasslands, with a diverse vegetation situated in an open landscape. We wanted to test this idea and to explore whether the assumed different flyways of the sexes could be related to sexual dimorphism, e.g. whether the smaller, shorter-billed females use other habitats than the males. This paper describes which meadow characteristics are correlated with meadow use and how meadow use differs between ruffs and reeves. In April and May 2003, 125 meadows in Southwest Friesland were monitored for five weeks. The total number of Ruffs decreased over the season, which is consistent with published region-wide counts. Relatively few females passed through: only in late April, when total numbers were low, the proportion females exceeded 10%. To find correlations with meadow use, 13 scored meadow characteristics were used in a multiple logistic regression model. Grass height and distance to the nearest roost proved most important (included in the model in four weeks): used meadows were closer to a roost and had shorter vegetation than unused meadows. Vegetation type, soil type, drainage level, openness of landscape and fertilisation freshness correlated with meadow use in two or three weeks. Percent flooding, fertilisation method, presence of grazers, vegetation evenness, relief and meadow size were never included in the model. The expected reference for peat meadows was not found: sand and clay soils were used more. As expected, ‘wet’ meadows and meadows in an open landscape were used more often than heavily drained meadows or meadows near buildings or trees from where predators may launch surprise attacks. Grass monocultures were least used, but the most used vegetation type was not rich but intermediately diverse in herbs. Females seem to be more extreme in meadow choice than males: groups with females used meadows that were drained less deep (thus wetter) and situated closer to the nearest roost than meadows with male-only groups. Groups with females were also more common in peat grasslands. We found indications that the sex-related differences in meadow use may be related to differences in feeding behaviour. Females foraged with higher pacing speeds. more females than males ate insects, but females had lower intake rates. Also when eating buried prey like earthworms and leatherjackets, intake rates in females were lower, although probing rates were equal. Females likely use other flyways: the proportion of females passing through this Dutch stopover site was very low compared with an important eastern European stopover site in Ukraine. At this point we can not yet decide whether this results from a difference in habitat preference induced by the size difference between the sexes or whether competition forces the females out of preferred, rich feeding sites.
