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Importance of riverine forests for
Collared Flycatchers (Ficedula albicollis) –
a study from Donau-Auen national park,
Lower Austria
Barbara M. Waringer, Karl Reiter, Christian H. Schulze
Department für Botanikund Biodiveritätsforschung, UniversitätWien, Rennweg 14, 1030 Wien, Österreich.
Introduction. The Donau-Auen Nationalpark southeast of Vienna covers
one of the last free flooding sections of the Danube river and it‘s
surrounding riverine forests (Fig. 1). It holds one of Austria‘s most
important occurances of Collared Flycatchers (Fig. 2). In spring 2015, we
examined the following questions, assuming that in high quality habitats
territories will be established earlier than in less suitable habitats:
What is the order the territories are established? What are the most
important factors for a high quality habitat in the Donau-Auen? Is there a
connection between early establishment, close distance to water and
insect density?
Results. Collared Flycatchers are very abundant in the survey area and could be observed at least once at the majority (87.8%) of points. The first individual
was observed on April 6, the main arrival started in mid April (Fig. 3). At 57% of points, we found a total of 84 territories within a 50 m radius resulting in a
population density of 7.28 territoris per 10 ha. Forest surface roughness was the best predictor for the occurance of territories (Fig. 4); a higher surface
roughness increases the probability for territories. Other important factors were the presence of Great Spotted Woodpeckers (negative effect), cavity
availability (positive effect) and standing dead wood (negative effect). There was a tendency of earlier territory establishment at points with higher surface
roughness compared to those with a more homogenous tree layer (Fig. 5).
Discussion. The observed density of 7.28 territories per 10 ha in the riverine forests southeast of Vienna is
surely over central European average. Since the 1980ies, the population seems to be stable in the lower
Austrian Donau-Auen (1983: 1,8-7,3 territories/10 ha, Windig & Steiner 1983 in Dvorak 2009).
A clear connection between food supply, distance to water bodies and habitat quality (Iwata et al, 2003)
could not be found. Surface roughness as best predictor could be an indicator for forest primevalness and
mirror the management history of the forest stands, respectively. The higher light influx within areas with
higher surface roughness could offer better foraging opportunities for Collared Flycatchers.
Our study shows not only the great importance of riverine forests for Collared Flycatchers but offers hints on
the high potential of remote sensing data for habitat analysis of forest bird species.
Forest surface roughness
Standing dead wood>20cm diameter
Number of woodpecker holes
Flying insects
Distance to permanent water bodies
Sum of individuals tits& nu thatches
Percent Fraxinus excelsior
Distance to open land
Sum of Dendrocopos major
individuals
Percent Populus alba
Mean forest age
Methods. From April 3 - May 24, 2015, multiple 5 min counts were done at
147 randomly chosen points. We visted each point 6 times to document the
order of occupation by Collared Flycatchers. Tits, European Nuthatches and
Woodpeckers were additionally counted to consider their potential role as
breeding competitors and/or cavity suppliers.
At the points, we measured standing dead wood, counted woodpecker holes
and calculated the density of flying insects. Forest type (soft wood vs. hard
wood forest) and forest age were obtained from data provided by
Österreichischen Bundesforste AG and MA 49 (township of Vienna). Distance
to water bodies and to open land was calculated using ArcGis 10.2. Forest
surface roughness (standard deviation of mean vegetation height in a radius of
50m) was obtained from data from a LiDAR surveying flight (available for 111
points). We used a model selection to detect important factors for territory
establishment (generalized linear models with territory incidence as response
variable).
Contact
Barbara M. Waringer
barbara.waringer@gmx.at
Thanks to
Karoline Zsak
Christian Baumgartner
Robert Zeiner
Monika Kanzian
Alexander Faltejsek
Fig. 1: Survey area (map of
Austria: basemap.at).
Fig. 2: Collared Flycatcher
male (Photo: Frank Vassen).
Fig. 3: Number of individuals per distance and survey round. Fig. 4: Model averaged importance of terms. Fig. 5: Mean surface roughness at territories with
different establishment-time.
Territory establishment until end of samplinground no.