Preliminary results from a study of habitat use of radio-tracked Spotted Crakes Porzana porzana at a restored wetland in northeast Jutland, Denmark

Abstract

Singing Spotted Crakes Porzana porzana were surveyed across c.16 km2 of restored peat cuttings in Lille Vildmose, northern Jutland, Denmark during summer 2013. Mapping of singing birds on 16 nights between 16 April and 9 July confirmed nine occupied “territories” based on the presence of between 0–6 birds on any one date. Singing Spotted Crakes were associated with shallower parts of peat extraction areas and flat restored areas with shallow (> 40 cm) water and dense vegetation. Singing birds were never heard in deep water channels, raised mire, dry peat cuttings, deep water peat cuttings, restored pasture, arable fields, dense willow carr or dense reed beds. Four radio-tagged Spotted Crakes (two males and a pair) were tracked from late May to early August during which time they exploited core home ranges of 0.33–0.56 ha. Vegetation samples within and around these home ranges showed crakes were present in most of the wetland vegetation types present, excluding very dry restored grazed grassland, areas dominated by Purple Moor-grass Molinia caerulea and Soft Rush Juncus effusus/Flote-grass Glyceria fluitans wet acidic grassland. In each of the areas used by tagged birds, quadrats within the minimum convex polygons plotted for each radiotagged individual had deeper standing water than those that were not used, but because of the variation in water levels between the three areas, they did not select for specific water depths across sites. There were no differences in the extent of open water, bare mud, dead vegetation or vegetation height between areas used and not used by tagged individuals. We conclude that shallow water retained throughout the summer is the most important feature of sites frequented by Spotted Crakes, with the depth of water and vegetation type/height being of secondary importance.