VAN DER HUT R, DIJKSHOORN D, HOOYMANS J, HYLKEMA J & VAN DE KAMP J (2016) Tracking Spotted Crakes Porzana porzana: calling activity and habitat selection in a Frisian peat bog. LIMOSA 89 (3): 97-107.
Habitat selection of Spotted Crakes was studied in Houtwiel,
a peat bog of c. 100 ha in the Dutch province of Fryslan.
The area consists of former meadows, where water tables
have been raised around 2006. Since then, vegetation is
dominated by Soft Rush and Sweet Reed Grass in shallow
water and by Common Reed along former ditches. Fields are
flooded in the winterperiod and dry out during summer. The
area is grazed by ponys and Highland cattle. Census visits
(twice a week during April-June) revealed 18-21 territories in
2012-2014 and 10 in 2015. Four individuals, two males and two
females, were caught and radio-tagged. Habitat data were
collected at calling locations, radio-tracking positions, nest
sites and random locations. Camera traps were used to study
The guidelines of the national breeding bird scheme led to
a considerable underestimation of the number of territories,
due to a low frequency of area visits (once in 10-14 days)
and criteria that disregard most April observations. Shallow
water, low vegetation stands, open patches and patchiness
appeared to be important habitat factors at calling and
foraging locations. Nesting habitat differed from foraging
locations by high vegetation cover; nests were built in
Soft Rush tussocks within low stands of Sweet Reed Grass.
Dynamic water tables and small scale relief affect vegetation
development and the availability of shallow water patches,
which are crucial for foraging. Grazing management seemed
to be important in creating patchiness in vegetation
structure by walking tracks and grazing patterns. Grazing
by Greylag Geese had a similar effect. The introduction of
dynamic water tables in meadows with small scale relief,
combined with grazing management, provide opportunities
to increase breeding numbers.
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