Spotted Crake habitat use 123
©Wildfowl & Wetlands Trust
Wildfowl
(2013) 63: 115–134
(including those obtained on the same day)
up to the point of their disappearance, it
seems that the attachment did not restrict
their activities during the study.
Small-scale differences in habitat use –
physical characteristics
Within each of their respective management
units, the quadrats sampled within areas
used by the radio-tagged Spotted Crakes had
deeper standing water than those that were
not (Table 2). However, because the water
levels within each of the management units
differed so much from each other (albeit
generally < 40 cm deep), it was not possible
to conclude that the crakes were selecting
for a given water depth at the time this was
recorded (17–20 June 2013). There was a
difference in the relationship between water
level and vegetation height in each of the
three management areas. All showed a
positive increase in mean vegetation height
at up to 20 cm water depth (Fig. 4), but in
the case of the crake territory nearest
Grønvej (Territory 1), vegetation height
decreased again in waters deeper than this
(Fig. 4), and plant cover likewise declined
with increasing water depth towards the
centre of open water bodies in this
management unit (Fig. 5). In the deepest
parts of these pools, individual
Typha latifolia
plants became conspicuously less common,
shorter and less robust, and vegetation cover
was eventually confined to a few submerged
macrophytes. Although vegetation height
was marginally greater in areas used
by crakes in Territory 1 and approached
statistical significance in Territory 2,
Table 1.
Summary radio telemetry data derived from the four tagged Spotted Crakes at Lille
Vildmose 2013. Territory number identifies the areas mapped in Figs. 1, 3a and 3b, with
number of independent positions derived (
i.e.
multiple fixes separated by intervals of > 90
min) divided between day and night (including dusk). The total number of days with
detections (out of 18 days between 31 May and 16 August when tracking was undertaken) and
the first and last dates are given together with the calculation of minimum convex polygons
for each bird using Ranges 8 v2.13 (Kenward
et al.
2008). The bird in Territory 2 made two
incursions into adjacent Territory 1 (see Fig. 3a), so the core area used by this individual is
indicated in parentheses excluding these longer distance movements.
Territory Sex Total
Night Day First
Last Number Minimum
number
number of fixes fixes date date of days
convex
positions
detected polygon (ha)
1
M 25
8
17 31 May 28 June 10
0.560
2
M 32
8
24 31 May 25 July 15
4.574 (0.258)
3
F
17
3
14 4 June 9 August
11
0.381
3
M 15
4
11 4 June 28 July
9
0.331
