130 Spotted Crake habitat use
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 115–134
areas. However, three birds sang from some
parts of the western and northern ridged
peat cuttings, although these were in areas
with less deep and more uniform areas of
standing water. We were surprised to find
that Spotted Crakes were absent from the
middle section of the restoration area,
which comprised a large area of essentially
open wet habitats with high water tables and
a mosaic of vegetation types, although these
areas did conspicuously dry out as June and
July progressed. Crakes were also absent
from the unsuitable dry rush dominated
pastures in the northeast, typically more
attractive to the Corncrake
Crex crex
, with at
least one bird singing there in 2013 (P.A.F.
Rasmussen, unpubl. data).
Smaller-scale habitat selection
The Spotted Crakes generally favoured areas
with standing water that remained shallowly
flooded during May–August, though more
frequent monitoring of water levels is
required to confirm water depths
throughout the season in these selected
areas. Beyond this, however, it was
extraordinarily difficult to tease out features
of the physical environment, the vegetation
and the habitat that were consistent and
which explained the crakes’ confinement to
the particular areas where we heard them
singing or otherwise located them by radio-
tracking. These observations are similar to
the findings of Schäffer (1999) and Gilbert
et al.
(2002), who found that Spotted Crakes
sang from shallow water areas less likely to
dry out during the course of the summer
than areas not used by the species, but
otherwise were difficult to assign to
particular habitat types. Although quadrats
within the minimum convex polygons of
tagged crakes had consistently and
significantly deeper water than quadrats
outside of these, the water depths varied
considerably within and between the
management units, so the absolute water
depths had little influence on where crakes
occurred. It may be no accident however,
that the radio-tagged crake in Territory 2 left
that area on a number of occasions and
latterly moved to Territory 1, given that the
ditch along which it had spent most of
May–June dried out more evidently than the
Typha
pools of Territory 1. This suggests
that a consistently high water level
throughout the breeding and brood rearing
period may affect the decisions of birds to
remain in an area or move elsewhere (as
previously reported by Schäffer 1999).
Measurement of the water table behaviour
throughout the breeding season therefore is
an important issue for future research, to
help explain such movements in birds that
otherwise show remarkable loyalty to
relatively small areas of habitat, and for
informing local habitat management
accordingly.
There was no evident association between
Spotted Crake site use and vegetation type,
as Fig. 6 indicates that the crakes were
present in almost all of the vegetation types
present, with the conspicuous exceptions of
the driest grassland vegetation, namely the
pure
Molinia caerulea
grasslands, the
J. effusus/
Glyceria fluitans
acidic wet grassland and
the predominantly terrestrial grasslands
(which had the driest substrate, was
subject to agricultural management and
disproportionately grazed by cattle), which
