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Habitat Selection of "Mad Cocks" of the Western Capercaillies Tetrao urogallus (Galliformes: Phasianidae) from the Fringe of the Range: A Case Study from Rila Mts. (Bulgaria)


Abstract and Figures

We investigated the habitat selection of "mad" Western Capercaillies males from the isolated and threatened Rila-Rhodope population. These "mad" Capercaillies are highly territorially aggressive individuals, that approach and attack people; this abnormal behavior, rarely occurs beyond single individuals in one lek and no studies that we know of have been published on such cases. In 2014-2015, we tagged with GPS transmitters three adult "mad" males associated with one lek. We evaluated the temporal variation in the Capercaillie habitat selection based on three periods ("summer", "winter", and annual). Based on Manly's selection ratios (design III), at the home range scale, males used measured habitat variables non-randomly. Birds selected forests dominated by Scots pine (annually) and Macedonian pine (summer). Males used forest stands in the age class "81 to 120" years more than the availability. They highly avoided stands dominated by Norway spruce, bare rocks and ski slopes, as well as forest stands less than 81 years old (summer and annually). The birds demonstrated significant avoidance of flat and highly slopped terrains as well as those with northern and northwestern exposure. Notwithstanding the abnormal aggressive behavior of Capercaillie males and their affiliation with an edge population, the habitat selection of "mad cocks" in the Rila Mts. is consistent with the principal habitat preference of the species.
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2020, Vol. 12, Issue 1 June 2020 pp. 155-169
Habitat Selection of "Mad Cocks" of the Western Capercaillies
Tetrao urogallus (Galliformes: Phasianidae) from the Fringe of the
Range: A Case Study from Rila Mts. (Bulgaria)
Dimitar G. Plachiyski* 1, 2, Georgi S. Popgeorgiev1,
Stefan G. Avramov2, Yurii V. Kornilev1, 3
1 - National Museum of Natural History, Bulgarian Academy of Sciences,
1 Tsar Osvoboditel Blvd., 1000 Sofia, BULGARIA
2 - Bulgarian Biodiversity Foundation, 39-41 Vesletz Str. fl. 4, ap. 11, 1202 Sofia, BULGARIA
3 - Integrative Zoology, Department of Evolutionary Biology, Faculty of Life Sciences,
University of Vienna, Althanstrasse 14, 1090 Vienna, AUSTRIA
*Corresponding author:
Abstract. We investigated the habitat selection of “mad” Western Capercaillies males from the
isolated and threatened Rila-Rhodope population. These “mad” Capercaillies are highly
territorially aggressive individuals, that approach and attack people; this abnormal behavior, rarely
occurs beyond single individuals in one lek and no studies that we know of have been published
on such cases. In 2014–2015, we tagged with GPS transmitters three adult “mad” males associated
with one lek. We evaluated the temporal variation in the Capercaillie habitat selection based on
three periods (“summer”, “winter”, and annual). Based on Manly’s selection ratios (design III), at
the home range scale, males used measured habitat variables non-randomly. Birds selected forests
dominated by Scots pine (annually) and Macedonian pine (summer). Males used forest stands in
the age class “81 to 120” years more than the availability. They highly avoided stands dominated
by Norway spruce, bare rocks and ski slopes, as well as forest stands less than 81 years old
(summer and annually). The birds demonstrated significant avoidance of flat and highly slopped
terrains as well as those with northern and northwestern exposure. Notwithstanding the abnormal
aggressive behavior of Capercaillie males and their affiliation with an edge population, the habitat
selection of “mad cocks” in the Rila Mts. is consistent with the principal habitat preference of the
Key words: Capercaillie, “mad cocks”, GPS devices, habitat utilization, resource selection.
The organization of animals in space
and time and the resource selection patterns
are central questions of ecology. Habitat
selection refers to a hierarchical process of
behavioral responses that may result in the
disproportionate use of habitats to influence
survival and fitness of individuals (Block &
Brennan, 1993; Jones, 2001). Understanding
how animals establish their home ranges
and how they select and use the resources
within the home range is crucial for
conservation and wildlife management
efforts (Rechetelo et al., 2016).
The Western Capercaillie Tetrao
urogallus L. (hereafter Capercaillie) is the
© Ecologia Balkanica
Union of Scientists in Bulgaria – Plovdiv
University of Plovdiv Publishing House
Habitat Selection of "Mad Cocks" of the Western Capercaillies Tetrao urogallus ...
largest and most dimorphic grouse of the
boreal and montane forests of Eurasia
(Rolstad et al., 1988; Storch, 2002). In the late
winter and spring, males establish
permanent ranges clumped around lek
centers, where they display and interact with
females in early spring, when the latter visit
the lek to mate (Wegge & Larsen, 1987;
Storch, 1997). After the display activity, in
early summer, Capercaillie males move to
distinct summer ranges and return to their
leks in autumn and winter (Rolstad et al.,
1988; Storch, 1995; Hjeljord et al., 2000). The
Capercaillie requires extensive areas and is
regarded as an important indicator of
intactness and high structural diverse of
mountain forest ecosystems (Grimm &
Storch, 2000). The species is habitat specialist
with affinity to old conifer forest (Storch,
2002). Due to its broad spatial and specific
habitat requirements, the Capercaillie is a
popular model species for the analysis of
species–habitats interrelationships
(Braunisch & Suchant, 2007). The
Capercaillie is an anthropophobic species
(Boev et al., 2007). However, throughout its
range, some male birds might exhibit an
abnormal aggressive behavior reaction,
resulting in approach and attack of humans
during the lekking period. These aggressive
Capercaillie males are referred to as “mad
cocks” (Storch, 2013). The aggressive
abnormal behavior can be regarded as stress-
coping responses (Jansen, 1986; Storch, 2013)
but there are no indications if it is related to
changes in habitat selection of birds.
The Capercaillie is a priority
conservation species because much of its
population is endangered and protecting
Capercaillie habitat will benefit a host of
other species of conservation concern (Suter
et al., 2002; Pakkala et al., 2003; Storch, 2007;
Mikoláš et al., 2016). As other endangered
populations, Europe’s southernmost
Capercaillie’s meta-population in the Rila-
Rhodope Massif, Bulgaria and Greece, is
threatened due to its low population size
(709–1185 displaying males in Bulgaria; 350–
500 individuals in Greece), isolation, habitat
degradation, and decreasing distribution
area (Storch, 2007; Boev & Nikolov, 2015;
Plachiyski et al., 2018). While the habitat
preferences of the Capercaillie are well
recognized in Scandinavia (e.g. Rolstad et al.,
1988; Rolstad & Wegge, 1989; Gjerde, 1991a,
1991b; Finne et al., 2000; Hjeljord et al., 2000),
Scotland (e.g. Moss et al., 1979; Picozzi et al.,
1996; Summers et al., 2004), Central Europe
(e.g. Storch, 1993a, 1993b, 1995; Saniga, 2002,
2004; Thiel et al., 2007), and the Iberian
Peninsula (e.g. Ménoni, 1991; Quevedo et al.,
2006; Blanco-Fontao et al., 2010; González et
al., 2012), the knowledge of the Rila-
Rhodope population is based only on direct
observations on the habitat use of the
species. Because populations at the edge of a
species’ distribution use ecologically
marginal habitats, observations made in one
part of the range are not always applicable at
the edge of a species’ distribution (Quevedo
et al., 2006).
We had the rare chance to identify and
to equip with GPS transmitters three “mad”
adult Capercaillie males associated with one
lek. We used GPS telemetry to understand
their habitat selection at home range scale.
The main questions asked were: (a) What is
the habitat selection in adult Capercaillie
males with abnormally aggressive behavior?;
(b) Did the habitat selection of adult
Capercaillie males with abnormally
aggressive behavior differ from the known
for the species in general? In addition, the
results obtained will indicate potential
differences in habitat selection between birds
from the southernmost edge and the others
populations that will inform conservation-
oriented management of the threatened
Material and Methods
Study area
The field study was conducted in 2014–
2015 in the northeastern part of Rila Mts.,
southwestern Bulgaria (Fig. 1). The study
area (defined precisely as a result of the
obtained telemetry data) encompassed 2162
ha of forests and glades from 1430 to 2330 m
Plachiyski et al.
a.s.l. between the upper wellsprings valleys
of the rivers Beli Iskar and Maritsa. The
climate is а montane variant of the
transitional, with mean temperatures of 0 to
14 °C in July and -7 to -4° C in January, with
annual precipitation of 700–900 mm. The
ground is usually covered with snow from
mid-November to late April or May
(depending on altitude and aspect)
(Kopralev, 2002). The forest communities are
represented by old (mean age 103 yrs. ± 35
SD; authors’ unpubl. data), open, mixed and
unmixed coniferous communities dominated
by Scots pine Pinus sylvestris L., Macedonian
pine Pinus peuce Griseb, Norway spruce
Picea abies (L.) Karsten, dwarf Mountain pine
Pinus mugo Turra and European silver fir
Abies alba Mill (Fig. 2).
The study area was situated
predominantly (1491.76 ha) within Rila
National Park (IUCN category II), managed
with priority on ecosystems diversity
maintenance and wildlife protection.
Hunting is banned. The remaining territory
(670.36 ha) was managed by the ski zone
concessionaire and local State Forestry.
Forestry activities included predominantly
harvesting, afforestation, protection against
erosion and floods, and hunting. In the
western part of the study area were the
infrastructure facilities (ski slopes, lifts, etc.)
of the “Borovets” Ski Resort. The resort is
located between 1300 and 2560 m a.s.l. The
skiing infrastructure included three ski
centers with 58 km marked ski trails as well
as ski roads, lifts (11.13 km), and roads
between the ski centers. In addition, 20 km
of mountain bike tracks were marked and
used predominantly during the summer
(Fig. 1).
Study of individuals and telemetry
In May and August 2014, three
displaying “mad” males (“Birds 1–3”)
associated with one lek were captured at the
lek using large fisherman’s landing nets and
by hand. According to beak depths (Moss et
al., 1979; Wegge & Larsen, 1987), all birds
were more than three years old. Two young
males displaying at the lek’s periphery were
identified but not captured.
Each of the three adults was equipped
on site with a “Bird 2A” backpack GPS tags
(e-obs Digital Telemetry, Grünwald,
Germany) and released. The devices were
fitted to the bird’s backs using a 5 mm Teflon
ribbon and a 3 mm thick neoprene pad glued
to the bottom of the device. The tags
weighted 88 g (2.5–2.75% of bird’s body
mass), provided positional accuracy of about
± 10 m, and could save about 10000 GPS
fixes. Timestamped readings were obtained
every 1 hour (in the displaying season) and 2
hours otherwise. Data were downloaded
wirelessly, with a maximum range of 200–
500 m in dense forest, 15 km hilltop to
hilltop, and 10 km by use of small plane.
Based on 18241 GPS fixes for the three
individuals (for “Bird 1” – 6638 GPS fixes in
428 days; for “Bird 2” – 5678 fixes in 357
days; “Bird 3” 5925 fixes in 362 days), we
obtained the Minimum Convex Polygons
utilized by each individual: “Bird 1” -
Annual 735.8 ha; Summer 604.12 ha;
Winter 110.33 ha; “Bird 2" - Annual
276.49 ha; Summer 187.96 ha; Winter
84.47 ha; “Bird3" - Annual 1138.95 ha;
Summer – 1117.51 ha; Winter – 136.61 ha.
Ethics statement
Strict protocols to minimize stress and
potential injury to the birds was followed.
Handling was minimal and all procedures
were carried on site by a veterinarian. The
scientific permit was issued by the Rila
National Park Directorate (№ РД–СР–
25/10.05.2014). At the end of the study, the
tags were removed and the birds were
released in good health.
Data analyses
To determine resource selection, we
used Manly’s selection ratios (w) for habitat
selection design III, where individual
animals are identified and both utilized and
available resources (resource units) are
measured at the scale of the individual
(Thomas & Taylor, 1990; Manly et al., 2002).
Habitat Selection of "Mad Cocks" of the Western Capercaillies Tetrao urogallus ...
Fig. 1. Study area in Rila Mts., Bulgaria,
with temporal distribution of the positions of the three “mad” Capercaillie males.
Fig. 2. Distribution of Land cover type, Age of Forest, Aspect and Slope within the study area.
Plachiyski et al.
The preference for a given habitat j,
given by its selection ratio wj, is the number
of times a Resource Unit (RU) within habitat
j was used, divided by the available number
of RUs for that given habitat. For our study,
all the RUs (8 m pixels) within an
individual’s MCP were defined as available.
According to the hypothesis of no particular
selection or avoidance, wj should approach
one, which means that the habitat j is used in
proportion to its availability (Bengtsson et
al., 2014). Habitat selection was defined as
the difference in recorded use (distribution
of GPS locations) to expected availability of
RUs using a log-likelihood chi-square test
(Khi2L) for overall habitat selection
(Calenge, 2019; Ramesh et al., 2016).
Capercaillie habitat preference was
computed using Manly’s habitat selection
ratios combined with 90% Bonferroni
simultaneous confidence intervals (Manly et
al., 2002). We considered significant habitat
preference if the lower CI limit was above 1
and significant avoidance if the upper CI
limit was below 1. Habitat preference
analyses were conducted by means of
“adehabitatHS” package in R (Calenge, 2007)
using a log-likelihood non-random statistic,
setting α = 0.05. We used software ArcGIS
ver. 10.2.1 (ESRI, 2014), in combination with
R version 3.5.1. (R Development Core Team,
2013) and R Studio version 1.1.463-2009-2018
(RStudio Team, 2015).
Environment definitions
Dominant tree species and forest stand
succession (Table 1, Fig. 2) were based on a
digital layer from the Forest Data Base (FDB)
(Executive Forest Agency, 2014). Non-
forested habitats were added based on
CORINE Land Cover level 3 (2012) and by
hand-delineating habitats using current
high-resolution aerial and satellite imagery
(Google Maps Hybrid, Google, 2019; World
Imagery Map, ESRI, 2019). The slope and
aspect (Table 1, Fig. 2) were derived from a
digital elevation model (DEM) with 8-m
resolution. The layers were rasterized into 8-
m pixels using the “feature to raster”
conversion tool and “cubic convulsion”
resampling in ArcGIS. All the environment
variables were turned into categorical and
reclassified either as equal size partitions or
using “Jenk’s natural breaks” function in
ArcGIS. To calculate individual habitat, use
and habitat selection, for each GPS location
we determined in ArcGIS the respective
habitat and surface characteristics.
To study the temporal variation in
habitat selection, the data were partitioned
conditionally into groups according to
distinct movements of tracked birds for
occupation of seasonal (winter–spring and
summer–autumn) habitats. A distinct
movement was defined as a directional
movement of 1 km or more within a 5-day
period (Rolstad et al., 1988). For each
individual, we defined the pre-displaying
and displaying period when the male birds
inhabit permanently the lek and the
territories around it and do not make distinct
movements more than 1.5 km from the lek
center, as “winter” (usually from December–
February to the first week of June). The
conditional “summer” (non-breeding)
period is then the remainder of the year
(usually second week of June to November–
January). The annual period then combines
the winter and summer.
At the home range scale (using MCP),
“mad” males used vegetation cover non-
randomly (annual: Khi2L = 5738.89, df = 14, p <
0.001; winter: Khi2L = 3773.28, df = 13, p <
0.001; summer: Khi2L = 3646.32, df = 14, p <
0.001). They significantly selected forests
dominated by Scots pine (annually) and
Macedonian pine (in summer) (Table 2, Fig. 3).
Habitats dominated by Dwarf Mountain pine
were used in proportion to its availability,
during summer and annually. Forests
dominated by Norway spruce, open (bare)
rocks and ski slopes were highly avoided
(Table 2, Fig. 3). Ski slopes were only present in
the summer home range ofBird 3”.
Roosters used forests of different stages
non-randomly (annual: Khi2L = 3492.57, df = 8,
Habitat Selection of "Mad Cocks" of the Western Capercaillies Tetrao urogallus ...
p < 0.001; winter: Khi2L = 2075.18, df = 8, p <
0.001; summer: Khi2L = 1670.1, df = 6, p <
0.001). They clearly avoided forest stands less
than 81 years old in the summer and annually.
Males used forest stands in the age class “81–
120 years more than the availability but the
selection was not significant (Table 2, Fig. 4).
Birds did not use slopes within the class
“63.1–73.0 (Table 2). In the summer, males
significantly preferred slopes within the class
“27.1–36.0 and avoided “0–9, “9.1–18.0 and
“54.1–63.0”. The birds also demonstrated
significant avoidance of flat terrains (“0–9.0”)
annually (Fig. 5, annual: Khi2L = 608.24, df = 17, p
< 0.001; winter: Khi2L = 1148.37, df = 16, p < 0.001;
summer: Khi2L = 906.54, df = 17, p < 0.001).
The roosters demonstrated significant
preference for southeastern exposure during
the winter and annually. They showed
significant avoidance of northern exposure
overall, as well as avoidance of north-eastern
aspect during the winter and southern
aspect during the summer (Fig. 6, annual:
Khi2L = 4671.87, df = 18, p < 0.001; winter:
Khi2L = 3909.04, df = 16, p < 0.001; summer:
hi2L = 3095.84, df = 18, p < 0.001). Despite
the high availability of northwestern
exposures (19.2%, Table 1), the birds did not
use them during the year (Table 2).
The large CIs for selection of variables
indicate individual variation in the
preference among the tagged birds.
Table 1. Availability of environmental variables within the study area. pix (n) = the
number of the pixels (8×8 m) within the corresponding variable class. ha = variable class area
in hectares. % = percent of pix (n) per variable.
Variable Variable class Available resource units
pix (n) ha %
Slope (Steepness, °) 0.0–9.0 16633 106.45 4.9
9.1–18.0 59498 380.79 17.6
18.1–27.0 108095 691.81 32.0
27.1–36.0 102046 653.09 30.2
36.1–45.0 38819 248.44 11.5
45.1–54.0 10756 68.84 3.2
54.1–63.0 1811 11.59 0.5
63.1–73.0 173 1.11 0.1
Aspect (Exposure) N 46607 298.28 13.8
NE 63798 408.31 18.9
E 65909 421.82 19.5
SE 22878 146.42 6.8
S 9144 58.52 2.7
SW 15263 97.68 4.5
W 49521 316.93 14.7
NW 64711 414.15 19.2
Forest stand succession (Age, years) 0–40 6217 39.79 1.9
41–80 9044 57.88 2.8
81–120 187246 1198.37 58.1
121–160 119750 766.4 37.2
Land cover: Dominant tree species Norway spruce (Ns) 134312 859.6 39.8
Macedonian pine (Mp) 95349 610.23 28.2
Dwarf Mountain pine (Dmp) 78345 501.41 23.2
Scots pine (Sp) 14251 91.21 4.2
Non-forest cover Grasslands (Gl) 6215 39.78 1.8
Ski slopes (SS) 4896 31.33 1.5
Open (bare) rock (OR) 4463 28.56 1.3
Plachiyski et al.
Table 2. Average selection ratios (Wi) at the home range scale for three Capercaillie
adult males. Legend: Ns = Norway spruce, Mp = Macedonian pine, Dmp = Dwarf Mountain
pine, Sp – Scots pine, Gl – Grasslands, Ski slopes (SS), OR – Open (bare) rock, SE = standard
error, ± 90% CI = confidence interval with lower and upper limits, Use % = habitat use, as %
of Capercaillie locations within variable class from total number of locations per variable.
Variable Variable class
Annual Winter Summer
Wi SE ± 90% CI Use
%Wi SE ± 90% CI Use
%Wi SE ± 90% CI Use
Slope (Steepness, °) 0–9.0 0.45 0.15 0.10 0.81 2.6 0.39 0.27 -0.28 1.06 3.8 0.35 0.11 0.08 0.63 1.8
9.1–18.0 0.93 0.05 0.80 1.06 16.7 0.95 0.10 0.70 1.20 27.5 0.54 0.11 0.27 0.81 9.4
18.1–27.0 1.00 0.05 0.88 1.11 32.2 0.81 0.18 0.38 1.24 29.8 1.05 0.08 0.84 1.25 33.9
27.1–36.0 1.14 0.11 0.88 1.40 33.4 1.44 0.35 0.58 2.29 26.2 1.27 0.07 1.10 1.43 38.3
36.1–45.0 1.03 0.24 0.45 1.61 11.4 1.65 0.45 0.54 2.76 8.1 1.21 0.49 0.02 2.40 13.6
45.1–54.0 1.06 0.24 0.48 1.64 3.3 3.81 1.99 -1.06 8.69 4.1 0.86 0.34 0.04 1.68 2.8
54.1–63.0 0.73 0.25 0.13 1.33 0.4 3.08 1.20 0.14 6.01 0.5 0.52 0.06 0.38 0.65 0.3
63.1–73.0 NA NA NA NA 0.0 NA NA NA NA 0.0 NA NA NA NA 0.0
Aspect (Exposure) N 0.48 0.2 0.1 0.9 7.1 0.32 0.3 -0.4 1.0 4.4 0.59 0.1 0.44 0.73 8.9
NE 0.84 0.4 -0.3 1.9 20.6 0.33 0.2 -0.2 0.9 6.0 1.26 0.6 -0.09 2.61 30.5
E 0.89 0.3 0.2 1.5 21.9 0.65 0.4 -0.2 1.5 19.8 0.96 0.4 0.07 1.85 23.3
SE 2.04 0.2 1.6 2.5 22.3 2.45 0.5 1.3 3.6 44.6 0.72 0.3 0.07 1.36 7.2
S 1.46 0.7 -0.2 3.1 9.5 2.06 1.2 -1.0 5.1 19.9 0.51 0.1 0.27 0.75 2.4
SW 1.82 0.6 0.3 3.4 8.9 0.40 0.3 -0.4 1.2 0.9 2.58 0.8 0.72 4.44 14.3
W 0.72 0.5 -0.4 1.9 9.8 0.59 0.4 -0.3 1.5 4.3 0.84 0.6 -0.51 2.20 13.4
Forest stand
succession 0–40 0.41 0.21 -0.06 0.89 1.1 0.78 0.53 -0.42 1.97 1.9 0.26 0.06 0.14 0.39 0.6
(Age, years) 41–80 0.37 0.21 -0.11 0.84 1.1 1.28 0.68 -0.24 2.81 2.5 0.05 0.05 -0.05 0.16 0.1
81–120 1.26 0.37 0.43 2.09 56.7 1.29 0.53 0.11 2.47 57.2 1.16 0.22 0.66 1.66 56.3
121–160 0.83 0.38 -0.01 1.68 41.2 0.75 0.45 -0.27 1.77 38.5 0.92 0.33 0.18 1.66 43.0
Land cover:Norway
spruce (Ns) 0.38 0.09 0.16 0.60 16.2 0.21 0.11 -0.06 0.48 5.4 0.54 0.14 0.19 0.89 23.5
Dominant tree
pine (Mp) 1.75 0.40 0.77 2.73 44.9 1.44 0.63 -0.06 2.94 34.6 1.92 0.24 1.34 2.51 51.9
Dwarf Mountain
pine (Dmp) 0.97 0.30 0.23 1.72 16.7 1.06 0.16 0.67 1.45 25.9 0.58 0.31 -0.17 1.32 10.5
Scots pine (Sp) 2.27 0.31 1.51 3.03 20.1 2.21 1.36 -1.04 5.46 29.4 1.92 1.36 -1.42 5.26 13.8
Non-forest cover Grasslands (Gl) 0.58 0.51 -0.67 1.83 2.0 0.39 0.32 -0.38 1.15 4.5 0.13 0.07 -0.04 0.29 0.3
Ski slopes (SS) 0.03 0.00 0.03 0.03 0.0 NA NA NA NA 0.0 0.04 0.00 0.04 0.04 0.0
Open (bare)
rock (OR) 0.08 0.06 -0.08 0.24 0.1 0.19 0.01 0.17 0.21 0.2 0.07 0.05 -0.05 0.18 0.1
Fig. 3. Vegetation cover selection by Capercaillie males at the home range scale in Rila Mts.,
Bulgaria. Ns – Norway spruce; Mp – Macedonian pine; Dmp – Dwarf Mountain pine; Sp –
Scots pine; Gl – Grasslands; SS – Ski slopes; OR – Open (bare) rock. Circles are Manley’s
Global Selection ratios’ mean selectivity rates; vertical bars are Confidence Intervals. Global
Selection ratios values > 1 denote habitats considered positively selected by the birds, while
those in the interval 0–1 are considered to be avoided.
Habitat Selection of "Mad Cocks" of the Western Capercaillies Tetrao urogallus ...
Fig. 4. Forest stage age selection by Capercaillie males at the home range scale in Rila Mts.,
Bulgaria. See Fig. 3 caption.
Fig. 5. Slope selection by Capercaillie males at the home range scale in Rila Mts., Bulgaria.
See Fig. 3 caption.
Fig. 6. Aspect selection by Capercaillie males at the home range scale in Rila Mts., Bulgaria.
See Fig. 3 caption.
Our results are the first to evaluate the
habitat selection of “mad” Capercaillie males
and the first to report on the Capercaillie
habitat selection in the Rila–Rhodope meta-
Land cover selection, forest age, and the
importance of old pine forests
The Capercaillie is adapted to climax
forests, with leks reportedly confined to such
mature, largely undisturbed habitats (Wegge
& Rolstad, 1986). Males prefer open-spaced
old forests throughout the year (Rolstad et
al., 1988; Gjerde & Wegge, 1989; Rolstad &
Wegge, 1987; Storch, 1993a, 1993b, 1997;
Picozzi et al., 1996; Saniga, 2002) and avoid
young forests (Rolstad et al., 1988; Gjerde &
Wegge, 1989; Storch, 1993a). Our results
agree with the studies from Scandinavia,
central Europe and Scotland indicating
general preference of old forests (81–120 yrs.
old), as well as clear avoidance of forests
80 yrs. old, both annually and during the
summer. The positive selection of forests 41–
80 yrs. old and the decreased avoidance of 0–
40 yrs. old forests in the winter could be
attributed to the territorial behavior of
roosters during displaying and the resulting
spatial distribution. We suppose that the
avoidance of forest patches 121–160 yrs. old
is predominantly due to them being
dominated by the highly avoided Norway
spruce (represented by 65.67% within the
age class). The association with old forest
fulfils basic needs for food and movement
Plachiyski et al.
(Summers et al., 2004) as well as anti-
predator behaviors (Finne et al., 2000).
Our results that Capercaillie adult
“mad” males habitat selection in winter is
principally determined by the strong
preference of old and pine-dominated forests
agree with previous studies (Wegge &
Rolstad, 1986; Rolstad & Wegge, 1987;
Gjerde & Wegge, 1989; Summers et al., 2004),
whereas continuous, homogenous spruce-
dominated stands (Gjerde & Wegge, 1989) as
well as open spaces (Finne et al., 2000;
Quevedo et al., 2006) are avoided. We
confirm the statements of several authors on
the habitat use of the species in Bulgaria
based on direct observations (Simeonov et
al., 1990; Ninov et al., 1994; Botev et al., 1998;
Boev et al., 2007).
Due to harsh weather conditions,
resource limitation and predators’ pressure,
the winter habitat selection of the
Capercaillie should be evaluated in terms of
predator avoidance as well as in an energetic
context (Storch, 1993b; Gjerde, 1991a, 1991b).
The Scots pine forest are the most common
winter habitat for species because the
combined availability of staple food and
shelter enables the birds to minimize the
duration of their activity periods (Lindén,
1981, cited in Thiel et al., 2007), and thereby
to minimize heat loss and predation risk
(Gjerde & Wegge, 1987; Storch, 1993b).
Mature trees’ needles have a higher energy
content than those of younger (Lindén,
1984). Old forests, such as the Scots and
Macedonian pine communities selected by
the “mad” males in this study, are
distinguished by their open structure
(Storch, 1993a). Unlike the avoided spruce
trees, old pine forests provide many single
trees with broad less dense crowns, with
large stout horizontal branches. These trees
offer enough space to fly in and are more
convenient for displaying, arboreal (day and
night) roosting and winter feeding (Moss et
al., 1979; Picozzi et al., 1996; Summers et al.,
2004). The depredation avoidance strategies
of Capercaillie males come down to 'detect
predator → escape' or 'detect predator → self-
defense' (Rolstad et al., 1988). Open forests
and open tree structures (typical of old
forests) are advantageous to detect predators
early on and to assess if defense or escape is
the appropriate strategy, as well as facilitate
detection of females during the mating
period (Moss et al., 1979; Botev et al., 1980;
Summers et al., 2004; Finne et al., 2000; Thiel
et al., 2007).
Predator avoidance patterns apparently
change between day and night (Thiel et al.,
2007). The major Capercaillie predators
martens and foxes (Schroth, 1991; Finne et
al., 2000; Jahren et al., 2016), hunt mainly
during the night. Martens willingly climb
trees and move by jumping between tree
crowns; thus, the Capercaillie preferred
roosting sites, solitary trees or trees in open
old stands, are usually isolated enough to
prevent this means of access (Thiel et al.,
2007). Within the study area the main tree
edifiers (Scots pine and Macedonian pine)
had a low projective coverage in the mature
forests where they dominate; this formed
complex communities with the participation
of a well-developed Dwarf mountain pine
layer and shrub phytocenoses dominated by
Common juniper Juniperus communis L.
During the day, when Capercaillie males
spend more time moving on the ground for
foraging, courtship and territory defense,
this dense understory of Dwarf Mountain
pine and Common juniper provides secure
shelter against detection by predators.
Habitat utilization in the summer
Capercaillie males face two main
problems in the summer to get enough
food to cope with the nutritional cost of the
molt, and to avoid predation (Rolstad et al.,
1988). In our case, as summer habitats
Capercaillie “mad” males strongly selected
old (81–120 yrs.) forests dominated by
Macedonian and Scots pines, and avoided all
other vegetation cover classes. Selected pine
communities were characterized by low
stocking density, determining availability of
well-developed field layer with high
abundance of Bilberry Vaccinium myrtillus L.,
Habitat Selection of "Mad Cocks" of the Western Capercaillies Tetrao urogallus ...
Lingonberry V. vitis-idaea L., Wild
strawberry Fragaria vesca L., Common
juniper Juniperus communis L., Raspberry
Rubus idaeus L., R. hirtus Walds & Kit.
(Rusakova, 2015; Dimitrov & Rusakova,
2015) and other plant species, taking
significant part in the Capercaillie diet
(Cramp, 1985; Simeonov et al., 1990; Storch,
1993a). The presence of a well-developed
ground layer provides shelter for birds when
they feed and rest on the ground. Due to the
dense canopy cover within much of the
spruce forests, there is almost no underbrush
and, in some cases, even a grass layer
(Rusakova & Dimitrov, 2015). In parallel,
spruce wood and mixed forests dominated
by spruces are the preferred habitat by major
Capercaillie predators such as the Pine
marten Martes martes L. (Sidorovich, 2011;
Spassov & Spiridonov, 2015). Therefore, the
lack of a rich trophic basis and an increased
depredation risk, possibly determine the
avoidance of this class of forest stands by
Capercaillie males.
Avoidance of open habitats
Avoidance of the open habitat types
(bare rocks, grasslands and ski slopes) by the
studied “mad cocks” could be considered a
predator escape strategy or disturbance
avoidance behavior. The Capercaillie is not a
permanent inhabitant in stands near centers
of human activities (frequented tourist
paths, ski slopes, etc.), although these
habitats also may fulfill its habitat
requirements (Saniga, 2002). The Capercaillie
probably use skiing areas only when
undisturbed refuges are also available
within their home ranges (Thiel et al., 2008).
Taking into account the clear avoidance of
ski slopes and the negligible presence of
“Bird 3” in suitable habitats adjacent to the
ski slopes during the summer (Fig. 3), we
could speculate that there was no available
undisturbed refuge within the ski zone in
our study area. The openings within the
forest are associated with habitat
fragmentation and edge effect. The increase
of grass and deciduous shrubs areas trigger
higher predator pressure on ground nesting
birds such as the Capercaillie (Rolstad &
Wegge, 1989). Forest edges and openings are
preferred hunting sites of the Northern
goshawk Accipiter gentilis L. (Storch, 1993a),
Pine marten and Red fox Vulpes vulpes L.
(Clevenger, 1994; Sidorovich, 2011), all
important predators of the Capercaillie
(Botev et al., 1980; Gjerde & Wegge, 1989;
Tornberg, 2001; Wegge & Kastdalen, 2007).
Topographical features
Some authors described preference for
upper slopes with NE, E, and SE exposures,
due to higher proportions of Bilberry on
east-exposed slopes (Botev et al., 1993;
Storch, 1993b). According to our results, at
the home range scale, Capercaillie males
most clearly avoided northern exposed
slopes, but excluding the significant
selection of SE slopes on annual basis; all
other results are difficult to interpret. We
consider the avoidance of northern
exposures as a consequence of the
distribution of the spruce-dominated
community, associated with convex relief
forms on northern exposures (Rusakova &
Dimitrov, 2015). Regarding the exposure of
the occupied terrains there is no regularity in
the distribution of the V. myrtillus
associations and it varies according to the
area occupied and the habitats specificity
(Vitkova & Rusakova, 2015). Therefore, our
results are in accordance with the
conclusions that the use of the different
categories exposure is predestined by the
aspect of the hills/valley axis as well as
according to the local weather conditions
(Saniga, 2002) and Capercaillie select
habitats independently of the exposure
(Rolstad & Wegge, 1987; Storch, 1993b).
Like Central European and
Scandinavian studies, our survey indicates
that hills and ridges are attractive
Capercaillie display grounds (see Saniga,
2002) but are also preferred terrain features
in the summer. Investigations from the
Teisenberg Mtn. identified general
preference for gentle slopes and avoidance
Plachiyski et al.
of steep terrains in winter, spring and
autumn that were less pronounced in
summer (Storch, 1993a, 1993b). In contrast,
our results indicate clear avoidance of flat
terrains (“0–9.0”), selection of gentle slopes
(“27.1–45.0”) during summer, as well as
preference of wider range (“27.1–63.0”) of
more steep slopes during winter. However,
in general, gentle slopes (“27.1–36”) seemed
to be preferred, most strongly pronounced in
the summer. The flat terrains within the
study area were dominated by grasslands
and dense Dwarf Mountain pine
communities, avoided by Capercaillie males,
which could explain why the birds were not
utilizing them.
Implications for management
Habitat management for the
Capercaillie should aim to provide forests
dominated by (or with significant presence
of) pines in the late successional stages with
open structure, low stocking density, and
well-developed understory with shrub and
grass communities for foraging and shelter.
Extensive cuttings, construction of firebreaks
and development of other forest openings
within potential Capercaillie habitats should
be avoided.
Notwithstanding the abnormal
aggressive behaviour of Capercaillie males
and their affiliation with an edge population,
the habitat selection of “mad cocks” in the
Rila Mts. is consistent with the principal
habitat preference of the species - old pine
dominated forest associations distributed on
hills and ridges. The selection of this
principal habitat is similar in winter and
summer. Thus, future studies can pool
results of “mad” and normal individuals,
and conservation initiatives should not
separate between the two types.
We are grateful to all people who
assisted us in the field, with special thanks to
I. Elenchev, K. Angelova and D. Dimitrova.
The study was supported by Project №
5103020-39-682 “Action plans for
Capercaillie, Three-toed Woodpecker and
White-backed Woodpecker”, developed and
implemented by the Bulgarian Biodiversity
Foundation and financed by Operational
Programme Environment 2007–2013. YK
was supported by an Erasmus+ grant.
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Received: 06.04.2020
Accepted: 07.05.2020
... Only few examples are given: ecological adaptations of Sylvia species in Bulgaria (SIMEONOV, 1975), ecological adaptation of dominant avian species in the planted monotypic coniferous forests (SIMEONOV, 1992), ecology of Pygoscelidae penguins in Antarctica (METCHEVA & TRAKIJSKA, 2002a), ecological ornithocomplexes in some parts of the Rhodopes Mnts. (NANKINOV, 1982b), ecological indices on the number and species diversity of birds along Danube River (PROFIROV, 1986), distribution and ecological requirements of Gyps fulvus (DOBREV, 2018), ecological requirements of Tetrao urogallus (PLACHIYSKI et al., 2020). The work of DONčEV (1958) is the most detailed study on the biology and ecology of all Bulgarian species of the Corvidae family. ...
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A short review of the main achievement and the most eminent workers on the birdlife in Bulgaria in the last 277 years is presented. A total of 46 fields/ aspects of bird studies are outlined in brief. Each research field is described in short with quotation of the first, the major, the most important or the most popular publications. Full references of these publications are given. The bibliography of the great many of them appears transliterated/ translated from cyrilic alphabet for the first time. The total number of the ornithological publications of Bulgarian authors and these on the Bulgarian birds is estimated as ca. 8000. The present work lists full reference data for 1/ 12th of them (691 items). Georgi Hristovich (1863-1926) is the first Bulgarian ornithologist. The number of Bulgarian workers in ornithology permanently increased and in 2021 it overpasses 100 specialists, advanced birdwatchers and bird-conservation NGO-s collaborators. Ornithology in Bulgaria has data for 739 bird species (421 recent and 318 known from their fossil/ subfossil remains) in the country. Avifaunistic is the oldest and most developed field of ornithological researches, while pterylogy is the youngest and less elaborated of their aspects. The countries of the Balkan Peninsula are the most studied foreign territories of Bulgarian ornithological research. Antarctica is the most remoted region, where Bulgarian ornithologists made their field researches. They contributed to the exploration of the birdlife of 68 states and territories all over the World. A total of 40 new avian taxa have been described from Bulgaria – 1 recent (Streptopelia decaocto) and 39 fossil (Miocene – Early Holocene), an important contribution to the World avian science. The oldest and the largest avian collection are stored at the National Museum of Natural History at the Bulgarian Academy of Sciences in Sofia. This institution always was and at present is, the most influencing research center in ornithology of Bulgaria.
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Detecting trends in the distribution and abundance of metapopulations is crucial to determining their status and to employ timely and effective measures for their protection. The ongoing increase of anthropogenic pressure requires obtaining precise data on the trends of the threatened Balkan capercaillie in Bulgaria. Therefore, we updated the species distribution data on a 10×10 km UTM grid and compared them with the results of a study of the distribution and abundance of the species we conducted in 2008–2015. Through field studies across the country, we identified 4,866 species locations. The literature data on former distribution covered 116 UTM squares. During the field study, capercaillies were located in 77 squares of the 10×10 km (159 squares of the 5×5 km) UTM grid, seven of which unknown so far. After 1890, the species has gone extinct from a total of 46 squares (39.7%). The isolated population in the Western Balkan Mts. has gone extinct; only sporadic observations of single, presumably non-breeding, individuals were made. The current population for Bulgaria is estimated at 709–1,185 displaying males. The mean number of displaying males, when using the maximum value for the population size, is 8.4 males per 5 km square (n = 141 squares) and 3.98 males per lek (n = 298 leks).
Conference Paper
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1. Winter densities of capercaillie in Scottish pine forests in 1975-7 varied from 5-36 birds/km2. 2. About 15% of the birds present were killed at a typical shoot. The number shot was closely related to the number seen and to the density of capercaillie. 3. Preliminary estimates of mean mortality rates are 39% for adult cocks and 59% for young cocks. 4. Capercaillie in natural forests were more numerous and bred better than those in planted forests. 5. The difference between natural and planted forests was attributed to a) more blaeberry and heather and b) the presence of mature "granny" trees in the open natural forest. Removal of "grannies" was followed by a marked reduction in the number of capercaillie. 6. It is suggested that forests of an open, natural character with a vigorous growth of shrubs may be shot over once a year without affecting breeding stocks. Typical planted forests with a close canopy of trees and a poor growth of shrubs may not be able to support the same shooting pressure. 7. The number of capercaillie present in the autumn at one forest was determined largely by the density of breeding birds in the previous spring and was scarcely related to the proportion of young in the bag.
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Declines in populations of capercaillie (Tetrao urogallus) and black grouse (Lyrurus tetrix) have been reported from both Central Europe and the continuous boreal forests of Fennoscandia. While intensified land-use is assumed to be the underlying cause of these declines, the mechanisms are not yet understood. Predation is the proximate cause of mortality of eggs, chicks and adults throughout ca-percaillie and black grouse ranges, but the link between predation and habitat and/or climate change remains unclear. To investigate temporal trends in reproductive output of woodland grouse, we collated previously published and unpublished data of reproduction in capercaillie and black grouse throughout their ranges from 1930 to 2012. We show that, overall, reproductive success has decreased and stabilized at low levels in most regions whilst capercaillie reproductive output in Scotland is still declining. With today's net reproduction, capercaillie and black grouse adult survival is too low to compensate for reproduction declines. Consequently, populations are expected to further decline unless reproductive performances improve. We put our findings in the context of changes in land use, climate and generalist predator numbers. By critically reviewing how these factors limit reproductive success in capercaillie and black grouse, we hope to shed light on the underlying mechanisms causing the decline. Our results imply that measures should be undertaken to reduce mortality of capercaillie and black grouse chicks and eggs. We suggest that future studies should aim to better understand which predators limit capercaillie and black grouse populations and how predation rates are mediated by continuously changing habitat and climate.
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ContextDistribution and connectivity of suitable habitat for species of conservation concern is critical for effective conservation planning. Capercaillie (Tetrao urogallus), an umbrella species for biodiversity conservation, is increasingly threatened because of habitat loss and fragmentation. Objective We assessed the impact of drastic changes in forest management in the Carpathian Mountains, a major stronghold of capercaillie in Europe, on habitat distribution and connectivity. Methods We used field data surveys with a forest disturbance dataset for 1985–2010 to map habitat suitability, and we used graph theory to analyse habitat connectivity. ResultsClimate, topography, forest proportion and fragmentation, and the distance to roads and settlements best identified capercaillie presence. Suitable habitat area was 7510 km2 in 1985; by 2010, clear-cutting had reduced that area by 1110 km2. More suitable habitat was lost inside protected areas (571 km2) than outside (413 km2). Habitat loss of 15 % reduced functional connectivity by 33 % since 1985. Conclusions Forest management, particularly large-scale clear-cutting and salvage logging, have substantially diminished and fragmented suitable capercaillie habitat, regardless of the status of forest protection. Consequently, larger areas with suitable habitat are now isolated and many patches are too small to sustain viable populations. Given that protection of capercaillie habitat would benefit many other species, including old-growth specialists and large carnivores, conservation actions to halt the loss of capercaillie habitat is urgently needed. We recommend adopting policies to protect natural forests, limiting large-scale clear-cutting and salvage logging, implementing ecological forestry, and restricting road building to reduce forest fragmentation.
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Habitat characteristics of 43 capercaillie (Tetrao urogallus) leks were studied in the mountains of Central Slovakia (West Carpathians) in 1984-2002. Macro-habitat was described with respect to topography and succession stage. Micro-habitat was described with respect to forest type and forest stand structure. Twenty-seven out of forty-three display grounds were situated in the upper half of the lateral ridges. Sixteen leks were located on hills of the lateral ridges (slope < 10%). All the leks were situated in old succession stages of the forest (80-200 years old). Twenty-seven display grounds were located in natural forests, sixteen leks were situated in man-managed stands more than 80 years old. Leks were situated in a variety of forest types with overstorey tree-density between 400-1,050 stems per ha. Distribution of leks was limited above all by macro-habitat characteristics (elevated sites, old stands). Age-space structure seemed to be a significant micro-habitat feature (preference of multi-layered stands).
Tetrao urogallus prefers pine needles with high energy and low resin (the ether-extractable fraction of needles) contents. There is a slight but significant correlation between the energy content of the needles and the age of the pine, which means that the lowered age structure of managed Finnish forests may prove to be a harmful environmental alteration. The male capercaillie forages mainly in the upper branches of the tree, while the female forages in the shelter of middle branches. The energy and resin contents of needles could not explain this sex-related foraging site difference.-from Author
This paper compares spacing behaviour of male and female capercaillie Tetrao urogallus in the German Alps, to those reported from the boreal zone, and discusses their implications for models of lek evolution. Based on 23 males and 13 females radio-tracked during April-May 1988-1992, the size, arrangement, and overlap of home ranges of males, and home ranges, lek visitation, and location of nest sites of females are described in relation to habitat, lek location, and the birds' age. Independently of sex and age, capercaillie preferred old forest habitats. With the exception of juveniles and some subadults that used large home ranges and visited several leks, males occupied permanent but overlapping territories clumped within 1 km of lek centres. Territorial traits were most pronounced in the oldest, dominant males: they used the smallest territories closest to the lek centre, used the central parts of their territories exclusively and showed the strongest site tenacity; nevertheless they tolerated subordinates within their territories. Females stayed farther from leks than males, most visited several leks, and nested at random distances from leks. Independently of habitat, multi-lek females used larger home ranges than single-lek females. The great variation in female home range size did not agree with Bradbury's hotspot and female-preference hypotheses, indicating that female home range size may be unsuitable in revealing clues about lek evolution in capercaillie.