115
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 115–134
Preliminary results from a study of habitat use of
radio-tracked Spotted Crakes
Porzana porzana
at a
restored wetland in northeast Jutland, Denmark
ANTHONY D. FOX
1
*, MARK DESHOLM
1
PALLE A.F. RASMUSSEN
2
& THORSTEN J.S. BALSBY
3
1
Department of Bioscience, Aarhus University, Kalø, Grenåvej 14, DK-8410 Rønde, Denmark.
2
Ryesgade 17, DK-9000 Aalborg, Denmark.
3
Department of Bioscience, Aarhus University, Vejlsøvej 25, DK-8600 Silkeborg, Denmark.
*Correspondence author. E-mail:
Abstract
Singing Spotted Crakes
Porzana porzana
were surveyed across
c.
16 km
2
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 radio-
tagged 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.
Key words
: habitat selection, Lille Vildmose, peatland restoration, vegetation types,
water levels.
