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UDK 630* 156 (001)



Miran ČAS*

ABSTRACT: Capercaillie (Tetrao urogallusL.) populations in central and
south-east Europe cover fragmented edge habitats and are recorded to decline
since 1960ies. Capercaillie leks in Slovenia are present at the south-eastern
edge of the Alpine metapopulation and at north-western edge of Dinaric.
These populations were monitored at leks in two periods in 1980 (466 monitored
leks) and 2000 (599). All leks were monitored by local specialists (hunters
and/or foresters) and main causes of observed lek populations decline were
addressed to each endangered lek. Special emphasis was given to predation at
leks, as suggested by D. Jenkins (2008). The six named reasons in 1980ies affected
39 leks with logging of old-growth forests (at 71.8% of leks) and construction
of forest roads (7.7%) as most pronounced. In 2000 nine reasons
affected 92 leks: (i) mountain tourism (26.1%), (ii) cutting of old-growth forests
(19.60%), (iii) predators attacks (18.5%), (iv) forest management in
spring time (9.8%), (v) pastures of livestock with wire fences in forests (6.5%),
(vi and vii) berries picking and overgrowing the last pastures in forest-landscape,
(viii) constructions of forest roads and (ix) infrastructure. The most
profound change in reasons between 1980 and 2000 mapping data were: predation
at leks, mountain tourism development, increasing of forest management
in spring time, wild pasturage of cattle and sheep in forests, overgrowing
the last pastures in forest-landscape. A comparison of the increasing percentage
of leks endangered by predators since 1980 has shown positive correlations
with increasing of the main predator populations’ densities. Population
density of martens (Martessp.) and wild boar (Sus scrofa) increased for 150%
since 1980, while red fox (Vulpes vulpes) density increased only after 1990.
Our results confirmed the assessment of reasons for threats to leks based on
descriptions and experiences of observers as a suitable approach for capercaillie
habitat risk assessment. Results for past decline and differences regarding
to the negative impacts on lek habitats are important guidelines for
foresters and wildlife managers concerning sustainable forest management
and maintenance of capercaillie populations.

Key words:Capercaillie (Tetrao urogallus), causes of leks endangerment,
predation, mountain tourisms, forest and wildlife management, rare
species population’s conservation


Capercaillie is a rare and endangered umbrella speet
al. 2002;Sachot etal. 2003;Angelstam 2004).
cies of temperate and boreal forests in Europe (Suter Capercaillie population densities are declining conti*
Dr. Miran Čas, Slovenian Forestry Institute, Večna pot 2,
1000 Ljubljana,,
nuously over the several last decades in Central Europe
(Klaus and Bergmann 1994, Čas 2006). Several
phone: +386 (0)1 20078 25
different habitat disturbances were recognised as cau

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ses of capercaillie decline in their distribution area in
temperate Europe (Klaus etal. 1997;Storch 1999,
2007;Saniga 2002, 2004;Thiel etal. 2007). Especially
at the population edges disturbances led to a severe
population reduction or to their complete
destruction (Poolo et al. 2005, Quevedo et al.
2006; Blanco-Fontao et al. 2009). Similar trends
were observed in temperate and in optimal boreal habitats.
In boreal forests the fragmentation of habitats due
to forest logging was recognised as the main cause of
population decline (Rolstad and Wegge 1987; Beškarevetal.
1995;Kurkietal. 2000;Angelstam
2004;Grafetal. 2007).

Capercaillie habitat in Slovenia occupies the southeastern
edge of its distribution range in theAlps (90% of
total habitat) and north-western edge in the Dinaric
Mountains (south-east Europe) (10% of total habitat),
con necting both large mountain regions (Adamič
1987; Čas 2006).Thecapercaillie habitats in Slovenia
can be found in old coniferous and mixed forests (spruce,
fir, beech) where leks are distributed in chains on the slopes
or in networks on forest plateaus (Čas and Adamič
1998;Purnat etal. 2005).The density of active
leks depends on the site suitability (Čas andAdamič
1998; Braunisch and Suchant 2008) and on the
conservation status and structures of the forest ecosystem
(Čas 2001).An observed mean distance (median)
among leks in the studied and representing suitable habitat
complexes is about 1.250 m between two lek centres
(ČasandAdamič1998;Purnatetal. 2007).

In general, capercaillie population size is decreasing.
Asevere drop of population for 37% (over 50%
decrease of active leks) on about 290 leks with active
subpopulations of about 1250 birds in year 2000 was
noted through the intensive monitoring in years 1980
and 2000 (Čas 2001).The hunting of capercaillie in
Slovenia was prohibited by Slovenian HunterAssociation,
since 1984, after the Bird directive (1979) and
was protected with law since 1993 (Official Gazette of
RS 1993/57) but the current population situation still
remains unsatisfactory (Čas 2001) and urges for a
deeper review of potential threats.

The aim of the study was to estimate main reasons
for a decline of active leks and role of predation in capercaillie
habitats shrinking and species extinct with
adapted forest and wildlife management.The study is
based on the population monitoring in years about
1980 and 2000.Available data on the causes for capercaillie
lek decline in the area of SlovenianAlps and Dinaric
Mountains was investigated, and a yearly
dynamics of predators and their removal from population
by hunting statistics was recorded and correlated
to lek decline. We gratefully accepted the idea for a
deeper review of potential causes of lek decline given
by an open email question raised in July 2008 by Prof.

D. Jenkins, the IUCN Grouse Specialist Group
member and researcher, who suggested a special focus
on the influence of animal predation at leks.

STUDYAREAAND METHODS – Područje istraživanja i metode rada


The study area covered about 20.000 km, mainly the
Alpine and the Dinaric habitats in Slovenia.Weincluded
all altitudes from the low elevation population at 400 m the high altitude at the forest line (about 1700 m
a.s.l.).The capercaillie population and decline was studied
in two 3-years periods with an aggregated data for
year 1980 and 2000. In the first period we analyzed 466
leks and in the second period 599 leks. Capercaillie leks
and subpopulations densities were monitored in several
research projects taking part at the Slovenian Forestry
Institute since 1980(Adamič 1987, Čas2000).

Disturbances at leks were noted as a descriptive parametres
of the monitoring questionnaire, where each
expert in fields stated the main reasons for lek or subpopulation
decline for each endangered or extinct lek.
All together 460 experts (hunters and/or foresters) studied
leks for three consecutive years in both monitoring
periods. Reasons for lek subpopulations decline or
dead were recorded. From available questionnaires we
extracted and summarised nine most frequent reasons

for lek subpopulation disturbance and damage (Table

1) and use them for comparison among monitoring pe

riods and statistics.

Tosupport predation as one of frequently stated reasons
for capercaillie population decline at leks, we analy sed
predator’spopulation density from hunting statistics
data, similarly as suggested by Adamič (1974) or
Storch etal. (2005).Available information on hunting
statistics for hunted (shot or otherwise removed) animals
from population were obtained from theAnnual
statistics reports of hunting game (Slovenian Hunters
Association / SHA/). Data for martens (Martes foina
Erx. andMartes martesL.), wild boar (Sus scrofaL.),
red fox (Vulpes vulpes L.) as potential predators were
analysed for 5 years corresponding to each capercaillie
leks monitoring period.The data for lynx (Lynx lynxL.)
and raptors removal were not analysed since only sporadically
named as a reason for lek disturbance.

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RESEARCH RESULTS – Rezultati istraživanja

3.1. Leks destruction – causes and dynamics – Uništenje pjevališta i dinamika

In years 1979-1981 39 (or 8.4%) out of 466 analysed
lek habitats experienced disturbance or destruction.
As the main reasons of capercaillie lek habitat destruction
in this monitoring period were: cutting of old-
growth forests (71.8% of disturbed or destructed leks),
building of forest roads (7.7%), overgrowing of pastures
in mountain forest areas (7.7%), berry picking
(5.1%), human disturbances of mountain tourism (recreation,
motor vehicles) (5.1%) and predators (fox,
martens, wild boar, lynx, etc.) (2.6%) (Table 1).

In the monitoring period 2000 92 leks were disturbed
or destructed (15,4% out of 599 monitored). Main
reasons for a lek disturbance or destruction were; different
forms of mountain tourism (26.1% of disturbed or
destructed leks), cutting of old-growth forests (19.6%),
predation at lek habitats (18.5%),forest management in
spring matting time (9.8%), pasturage of cattle and
sheep in forests (namely the dangerous are wire fences)
(6.5%), overgrowing of pastures in mountain forests
(5.4%), berry picking (5.4%), construction of forest
roads (4.3%), and infrastructure building activities
(electricity cords) (1.1%) (Table 1).

The comparison of both monitoring periods (Table 1)
revealed differences in lek disturbance or destruction
causes which were correlated with the following improvements:
a decrease in the cutting of old-growth forests
at leks (-52.2%), and a minimum decline of impact of
forest roads construction (-3.3%).The deterioration in
habitats showed an increase in the negative impact of
mountain tourism (with 21% increase among years) and
increase of the negative predator impact (15.9%). Other
lek disturbance or destruction causes showed lower increase
among the two monitoring periods.

Table 1
The most frequent causes of capercaillie lek disturbance or destruction as revealed from 1980 and 2000
monitoring periods questionnaires

Tablica 1.Najučestaliji razlogi za poremečaj ili uništavanje staništa tetrijeba u godinama 1980 – 2000,
dobivenih na osnovu upitnika

Impacts at leks’habitats
Number of
disturbed or
in 1980
disturbed or
leks (%) in
years 1980
Number of
disturbed or
in 2000
disturbed or
leks (%) in
years 2000
Difference among
two monitoring
periods, expressed
as a % of change
in regard to 1980
monitoring period
Cutting of old-growth forests 28 71.8 18 19.6 -52.2
Construction of forest roads 3 7.7 4 4.3 -3.3
Infrastructure (electricity) 0 0.0 1 1.1 +1.1
Forest management in spring time 0 0.0 9 9.8 +9.8
Mountain tourism (recreation,
motor vehicles, etc.)
2 5.1 24 26.1 +21.0
Predators (fox, martens, wild boar,
lynx, raptors, etc.)
1 2.6 17 18.5 +15.9
Berries picking 3 7.7 5 5.4 -2.3
Pasturage of livestock in forests,
wire fences
0 0.0 6 6.5 +6.5
Overgrowing of pastures
in mountain forests
2 5.1 5 5.4 +0.3
Overall number of disturbed or
destructed observation leks
39 92

3. Lek predators and predation level – Predatori na pjevalištima i razina predatorstva

Acomparison of the increasing percentage of leks 2.5 animals/1000 ha and for wild boar from 0.8 to 2.0.
endangered by predators and trends in density of hunted The hunting dynamics of red fox showed a slight depredator
animals in Slovenia showed a positive correla-crease for 18% in the same period.The population dynation
with capercaillie leks disturbance and destruction in mics of red fox is suggested to be under a cyclical
20-year time among the two monitoring periods (Table population changes trends causing an increase of popu2).
Trends of population dynamics of all three main pre-lation and changes in hunting (to 3.5 hunted anidator
species were positively correlated with lek preda-mals/1000 ha) and a negative impact on the capercaillie
tion. Density of hunted martens increased from 1.0 to leks vitality was expected to start only after year1990.

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Table 2 Density of shot predator animals in Slovenia (1980–2000) (animals / 1000 ha)

Tablica 2.Gustoća odstrijeljenih jedinki u Sloveniji (1980–2000) (broj jedinki / 1000 ha)

Predation species
of wildlife
Average in 1980
(5 years) (shot
animals/1000 ha)
Average in 1990
(5 years) (shot
animals /1000 ha)
Average in 2000
(5 years) (shot
animals /1000 ha)
Trend of
Change of density
of shot animals
in age 1980–2000
Marten (Martes martes,
M. foina)
1.0 2.2 2.5 + +150%
Red fox (Vulpes vulpes) 4.3 2.6 3.5 + 18%
Wild boar (Sus scrofa) 0.8 1.8 2.0 + +150%


Cumulative results indicated high negative impact
on lek habitat suitability in the several main clusters of
reasons (Table 1, 2).

The main reasons for the decline in capercaillie population
density over the two decades since 1980 were
studied at leks and the endangerment by predation of
red fox, martens and wild boar were correlated with the
hunting statistics data. Research has included the area
of a suspended habitat corridor in the Central European
distribution range in Slovenia (Čas2006).Analyses of
data from lek monitoring questionnaires confirmed the
assessment of leks threats reasons on the basis of the
descriptions and experiences of observers as a good indicator
of the causes of risk habitats. Observations of
leks showed several causes for population decline. Different
land use on mountain landscapes and predator
densities turned out to be the main reasons causing a
gradual destruction of past subpopulations and their
retrieval to habitat remains of mix conifer forests in
colder and less accessible areas (Čas 2006; Čas and

An important cause of lek subpopulations died turned
out to be predation.This is one of the third main
reason for disturbance and destruction of lek habitats.
From 1980 to 2000 the predation at observed leks in
Slovenia raised from 2.6% to 18.5% (Table 1), mainly
ue to the habitat fragmentation (Kurki et al. 2000;
Andrén 1994) and an increase of predator populations
densities;Storchetal. 2005; Čas2006). Changes
of land use, nature conservation policies, hunting
management, a sustainable nature use and changes in
rural society structure and functioning in post industrial
society in various ways promoted predator species
(Angelstam etal. 2001; Čas 2001, 2006).With the
adoption of the Birds Directive (1979) and Habitat Directive
(1992), hunting of all raptors’species was banned
in Slovenia (Official Gazette of RS 1993/57). The
ban coincided with a decline in the popularity of fur
clothing.These actions changed the attitude and behaviour
of hunters towards predators as the important regulator
of grouse population densities. Population
density of many rare or generalist species of grouse
predators (fox, martens, wild boar, raptors, raven) therefore
(cyclically) increased (Lindström etal. 1994,
Budiansky 1995,Klaus etal. 1997, Cattadori and
Hudson 2000, Storch et al. 2005) and showed a
higher impact in predation at leks and a weaker breeding
success (Storaas et al. 1999, Saniga 2002,
Baines et al. 2004; Merta et al. 2009). The frequently
observed predator noted with a prey at observed
capercaillie leks were red fox, martens, lynx and
sporadically goshawk (Accipiter gentilisL.) and eagle
(Aquila chrysaetosL.). In one case lynx was noted as a
sporadic predator in 1980 at a single lek in Dinaric area
of Slovenia following its re-introduced (1973).Animal
killed all three males at one lek.This establishment of
predator pressure was confirmed by a pilot study of
predator tracks of red fox, martens and lynx in snow at
four capercaillie leks in SlovenianAlps (Dretnik et
al. 1999; Čas 2000). Observed lynx tracks were caused
by only one lynx pair yet, seen at the 20,000 hectares
area (which confirmed their mysteriously life and
waylaying strategy of plunder at promising locations).

The observation of predation at leks increases between
1980 and 2000 showed similarities with an increase
of negative influence of the few main predator of
wildlife populations’ density increase for 150% (martens,
wild boar) (Table 2). Population dynamics of red
fox showed a slight reduction in density (-18%), but the
data suggest the negative influence of cyclical trend of
33 –year cycle with minimum in 1990 and increase the
density of population about year 2000 (to 3.5 shoot animals/
1000 ha) (Čas 2006). However, the habitat fragmentation
and negative impact of red fox on capercaillie
population size after 1990 has increased, similar to the
martens and wild boar increase in Alps after 1980
(Storch etal. 2005; Čas2006).Additionally we assumed
the predators as one of the main reasons for capercaillie
density decline in open forestland in this part of
Europe. In summary we assumed a negative correlation
between predator species densities by hunting statistics
and capercaillie population density, as prey.

The predator pressure at leks has shown adapted
strategy for survey of capercaillie birds.The behaviour
of capercaillie birds caused by predator confirmed to
influence the fear of the subpopulation activities and
the change of the mating time at leks. In case of one
continuously observed lek with approximately five ac

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tive cocks in theAlpine region in north Slovenia we
established avoidance of beginning of display of cocks
on the ground to higher visibility in light early morning
in later time due to predators waiting at ground (martens,
fox) before in darkness (Čas,unpublish). Interesting
and important was the surmise that behaviour and
shift of capercaillie birds out of the mating leks do not
take regard of the predators (Elliason and Wegge
2007). On the other hand predation as a cause of lek
disturbance occured very seldom on Norwegian leks.
But both males and females were taken by predators
during daytime when they were not on the lek (P.
Wegge,pers. comm. 8.Aug. 2008).

The first important parameter of lek habitats suitability
in management forest landscape are suitable structure
with above 60 to 80% of opened mature and old
forests with gaps and with sufficient share of pasture
areas (3–5%) with berries and with persistence of sufficiently
high percentage of conifers in mixed forests
(60–95%) (Storch 1999; Čas 2006).There are habitat
suitable rich field layer (above 60%) with bilberry
(Eiberle 1984;Storch1999;Bolmanetal. 2005;
Graf etal. 2007). In old forest habitats are important
persistence of liying trunks and ant hills (Čas 2006).
Comparable results were obtained for other capercaillie
habitats in Eurasia (Rolstad and Wegge 1987,
Beškarev et al. 1995; Klaus and Bergmann,
1994; Storch 1999; Saniga 2004). Since 1960ies
Slovenia experienced intensive thinning in co-natural
multipurpose forest management and intensive opening
of mountain forests with forest roads to between
1980–1990ies (Robek andKlun 2007). In that time
many leks were destroyed as a result of the cutting of
old-growth forests. It coincided with an account for a
high percentage (71.8 % in the reason responsible) of
active leks decline around year 1980. Later, the effect
of cutting decreased to 19.6% leks and the effect of
construction of forest roads from 7.7% to 4.3% leks
around in 2000.This phenomenon is confirmed by the
fact that forest road construction in Slovenia rose strongest
by 63.7% gradually between 1964 and 1989 up to

19.8m/ha (ReNGP, Ur.l. RS, 111/2007). Intensified the

forest management in mountain forests considerably

caused temporary destruction of habitat and its frag

mentation and other human disturbances impacts on
capercaillie habitat reduced (Adamič 1987, Čas
2006); and similarly is in other countries of capercaillie
distribution (Rolstad and Wegge 1987; Beškarevet
al. 1995;Storch1999;Zubić2009).

Additional negative human impacts in habitat were
caused by forest management in spring matting and
breeding time, pasturing of cattle and sheep or wildlife
and berries picking (Table 1) which negative impact on
persistence of bilberry food and breeding success were
confirmed in other studies (Baines etal. 2004; Purnat
et al. 2005). In recent times cables of pasture fences
turned out to have negative influence on
capercaillie as well (Catt etal. 1994). In addition a natural
forest development to more deciduous structures
and the habitat of mix coniferous forests shrinking due
to the climate change and temperature increase was obvious
in Slovenia (Čas andAdamič 2007;Kutnar
et al. 2009) and wider in Europe (Fanta 1992;Stutzer
2000; Marrachi et al. 2005). Overgrowing of
last pastures in mountain management forestland was
indicated as an additional cause of leks endangerment
observed in Slovenia.

The second main negative impact on the suitability
of capercaillie and also black grouse (Tetrao tetrix) habitats
in Europe were mountain tourist activities
(Storch 1999, Gulič et al. 2005; Menoni et al.
2006;Thiel etal. 2007).After an opening of mountain
forests with forest roads to the 1980ies, areas became
favourite spots for mountain tourism including
motor vehicles and snow sledges driving.This impact
on lek abundance was reflected in an increase of endangered
leks from 1980 to 2000 (+21.0 %) (Table 1). The
human disturbances on the edge of capercaillie distribution
area and habitat fragmentation in parallel to climate
changes and air pollutions impacts on habitat
changes to unsuitable structures influenced capercaillie
population in studied forests (Čas andAdamič 1995,
Storch 1999, 2007; Angelstam et al. 2004;
Pooloetal. 2008;Thieletal. 2008).

AND WILDLIFE MANAGEMENT – Zaključci i prijedlozi za
adaptaciju šumskog i lovnog gospodarenja

The sustainable dynamic of majority percentage of
mountain old-growth mix forest in areas with a modera te
road density and unaggressive and controlled mountain
tourism was important for conservation of capercaillie
habitat suitability. Predator number control (hunting of
predators) (Budiansky 1995) in the capercaillie lek
areas and the nature of coherent population density of
predators were crucial regulators of stable grouse densities
in mountain forest landscapes of Central and South-
East Europe (Storch etal. 2005; Čas2006).This analysis
showed that the assessment of the reasons for threats
to leks on the basis of the descriptions and experiences of
observers as a good indicator of the causes of risk habitats.
Results of the current situation and differences regarding
the negative impacts on habitats were an important
guideline for forest and hunting management planning,
and for a sustainable multipurpose landscape use with a
continuous presence of forest grouse species.

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On the base of comparable research of another pre da-experiment at two hunting districts at Koprivna and Bi


tor species (red fox), influencing to the roe deer
(Capreolus capreolus L.) population density with a negative
impact on population dynamics (Čas 2008) we
suggested that forest grouse species (capercaillie, black
grouse, hasel grouse Bonasa bonasia L.) to be under
strongest predator pressure too. Negative influences of
red fox, martens and wild boar population dynamics on
capercaillie population density was confirmed by results
of significant cyclically relations from hunting statistics
data in Slovenian lands since 1874 (Čas 2006). Confirmation
in this study (Table 1, 2) permits predator number
control (predator control) in these hunting association
areas as urgent wildlife management measure for sustainable
capercaillie (and roe deer) stabile populations
(Budiansky 1995).

In past two years the suggestion of predator control
(Čas 2008) resulted in positive consequences in a pilot
stra valleys (104.3 km).This narrow study areas represented
optimal site for capercaillie habitats within a
larger area of Koroška (Carinthia) in northern Slovenia
(Peca – 2.126 m a.s.l. and Smrekovec – 1.684 m a.s.l.
mountain). Our solution of predator control through the
granting of hunters with one premium offspring roe deer
or chamois for each ten foxes or five martens shot in one
hunting season resulted in succesfull control with a total
of up to four times increased number of shot foxes or
martens per year.The increase of shot predators was most
pronounced in winter time when the population is in general
most vulnerable for density changes (Sandercock
2010) as it used to be in past times with a good
sale of fur from these predators.Now a higher density of
forest grouses and roe deer were observed in that area.


The text preparation were supported by the Forest
Biology, Ecology and Technology Research Programme
(P4-0107), financed by the Slovenian ResearchAgency
and V4 0175109 (1998-2000), V4-0492 (2008-2011)
and V4-0497 (2008-2010) research projects funded by
the Ministry ofAgriculture, Forestry and Food of the Republic
of Slovenia (RS), the Ministry for Science and
Technology of the RS, and the Ministry of the Environment
and Spatial Planning of the RS.Wethank to hunters
and foresters from the Slovenian Hunting Association
(SHA) and the Slovenian Forestry Service (SFS) for their
efforts at fieldwork on capercaillie birds counting and
leks observations. We would like to thank Prof. Miha
Adamič from Biotechnical faculty, Dep. of forestry in
Ljubljana and to Prof. Marijan Grubešić from Forestry
faculty in Zagreb for support in research, Dr. Primož
Kmecl and Cilka Zupančič and especially to Dr. Tine
Grebenc from the Slovenian Forestry Institute for fruitful
cooperation on this paper.

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SAŽETAK: Populacije tetrijeba (Tetrao urogallusL.) u središnjoj i jugois toč
noj Europi obuhvaća fragmentirani rub staništa,. Brojnost je u opadanju
još od 1960. Staništa (pjevališta) tetrijeba u Sloveniji prisutna su na jugois toč
nom rubu alpske metapopulacije i na sjeverozapadnom rubu dinarske metapopulacije.
Te populacije praćene su na pjevalištima u dva razdoblja, u
1980. g. (466 praćenih lokaliteta) i 2000. g. (599). Svi lokaliteti pratili su lokalni
stručnjaci (lovci i / ili šumari). Promatrali su glavne uzroke pada populacija
u staništima, koje su utvrdili za svaki ugroženi lokalitet. Poseban
na glasak istraživanja bila je predacija staništa, kao što je predložio D. Jenkins
(2008). Glavni razlozi (od šest) ugrožavanja pjevališta (39 pjevališta) u
1980. g. bili su: sječa starih šuma (na 71,8 % lokaliteta) i izgradnje šumskih
cesta (7,7 %) i branja šumskih plodova (7,7 %), dok je u 2000. g. bilo devet
razloga na 92 ugrožena lokaliteta: (i) planinski turizam (26,1 %), (ii) sječa
starih šuma (19,6 %), (iii) predatori (18,5 %), (iv) šumski radovi tijekom proljeća
(9,8 %), (v) ispaša stoke u šumama, žičane ograde (6,5 %), (VI i VII)
branje šumskih plodova i zaraštanje pašnjaka, (viii) izgradnja šumskih cesta i

(ix) ostale infrastrukture. Najznačajniji razlozi promjena i ugrožavanja staniš
ta između 1980. i 2000. g. bili su: razvoj planinskog turizma, predatora na
staništima, radovi u šumama u proljeće, divlje pašarenje goveda i ovaca u šu-
mama, zaraštanje posljednjih pašnjaka u šumskim područjima. Usporedba
po većanja postotaka ugroženih lokaliteta od grabežljivaca od 1980 godine
pokazala su pozitivne korelacije s povećanjem gustoće populacija glavnih
grabežljivaca. Gustoća naseljenosti kuna (Martes spp.) i divlje svinje (Sus
scrofa) porasla je za 150 %, dok se gustoća naseljenosti lisice (Vulpes vulpes)
povećala od 1990. g. (za 35 %). Naši rezultati potvrđuju ocjenu uzroka negativnog
utjecaja na pjevališta, a temelje se na opisima i iskustvima promatrača
kao prikladan pristup za procjene rizika za staništa tetrijeba. Spoznaje o uzrocima
sadašnjeg pada pojavnosti tetrijeba nameću donošenje smjernica koje bi
omogućile promjenu načina gospodarenja šumama i divljači u cilju podizanju
kvalitete staništa za ovu vrstu.

Ključne riječi:tetrijeb (Tetrao urogallus), uzroci ugroženosti staništa,
predacija, planinski turizam, gospodarenje šumama i lovištima, zaštite populacija
rijetkih vrsta