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Bird Statistics
Western Capercaillie -
Tetrao urogallus
The Capercaillie is the largest grouse in the
world, adult males measure 86-95cm (with a 29-40cm tail), can have a wing span of as much as 125cm and weigh around
4-5Kg. Females are smaller, measuring around 56-65cm (with a
16-21cm tail) and only weigh around 2Kg. The two sexes do
not appear similar, from a distance the male looks all dark with
some complex plumage where the female is brownish and chestnut
with black and white barring. With young Capercaillie the
darker colouring can become apparent from around the second month
of their life.
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Adult Male
At a distance male Capercaillie appear mainly dark slate-grey,
but lower head, flanks, belly and tail are almost black, his
chest is glossy green-black and upper mantle and wings convert
to dark warm brown. White of pale grey marks interrupt
the general darkness of the plumage at the shoulders, along
the flanks, tail-coverts and as speckles on the centre of
outer tail-feathers. |
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Adult Female
Rufous-brown on the back, chestnut on her chest
and slightly paler elsewhere. There is heavy black barring
above and black and white barring below, particularly on the
flanks. The barring is absent on across the centre of the
chest, making the chestnut patch there noticeable. Her
wings are coloured as the upper body, without any wing bars.
Her tail is broad and distinctly rounded with irregular chestnut
and black barring.
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Juvenile Capercaillie
Juvenile Capercaillie are similar to females, but smaller and
have duller colouring. Males begin to develop a darker
plumage after about eight weeks, although by their first
winter the juvenile male has similar plumage to the adult they
are distinctly smaller.
The hatchling is
at a distinct disadvantage as they
cannot thermoregulate ( maintain a stable body temperature) for the
first 4-6 weeks. The Juvenile will develop quickly from
hatching - depending of course on good weather conditions and a high
protein diet (consisting of an abundance of insects). At
approximately 3-4 weeks of age, the young will be able to perform
their first flights, albeit over short distances. At the age
of about three months the juvenile will moult for the second time,
at this stage their sub-adult plumage will be visible and the two
sexes can be distinguished easily.
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In spite of it's bulk, the Capercaillie is very
agile, flying easily within woodlands and in and out of the
canopy. When initially escaping from cover Capercaillie can
be very noisy, but when in full flight they are near silent,
normally flying within woodlands or just above the tree tops.
Although they are normally quiet birds, during
the breeding season both sexes become vocal - the males lekking
calls being the most recognisable. In springtime, male congregate at places in the forest called 'leks' and sing and display to impress the females. The song, much of which is inaudible to humans, carries for several kilometres to attract females. The most dominant male on a lek, called the 'Alpha' male, mates with most of the hens. Not surprisingly, males sometimes fight for this position!
(Download and listen to our sound clip of the male Capercaillie at the bottom of the page.)
Habitat
The Capercaillie has adapted itself to thrive in
a habitat dominated by old coniferous forests coupled with a dense
cover of ground vegetation. This ground vegetation is of the
Vaccinium species. This contains the likes of
blaeberry, which Capercaillie depend upon heavily as a source of
nutrition from early spring through to summer. The best
habitats tend to have a light canopy, allowing ample sunlight to
penetrate through the trees to the ground vegetation (heather and
blaeberry). This ground vegetation provides not only
nutrition for the Capercaillie in the form of it's fruit and
invertebrates, but also in the form of ground cover from both
predators and adverse weather conditions. The Capercaillie
is a specialist in this type of habitat. Breeding
Depending on three different factors
(weather conditions, vegetation development and altitude) the
breeding season begins between March and April and lasts until about
May or June. The majority of this mating season is taken up
with the territorial competition between rival cocks.
In Scotland Capercaillie prefer mature Scots pine forests with an undergrowth of heather
and blaeberry, leks are often sited in more open areas of woodland and
although they are often in the same area, they can sometimes move around from year to year.
It is only towards the end
of the breeding season that the hens arrive at the lek sites.
At this point the males will join the hens on the ground, flying
down form his courting tree where he has performed a variety of
songs. The cock will continue his display of song and dance
on the ground, this is the main courting season. If there is
more than one cock present at the lek, then the alpha male will
tend to copulate with the majority of the hens. However, the
alpha male will often not achieve this without some level of
direct confrontation with rivals. These confrontations are
sometimes so intense that they do not stop until one of the rival
cocks is dead. Alpha males tend to be older, have the
greater body size and the broader tail fan. Understandably,
they will be dominant and therefore mate with the majority of the
females.
Wintering
The Capercaillie winters in similar habitats to those used in summer months. However young, dense areas of trees can also provide additional shelter in bad weather.
The cock will venture onto the ground more than the hen during the
winter period, and thus, if tracks are spotted in the snow or
ground during the winter months, they are most likely to belong to
a cock.
Where to find it
Most commonly resident in native pinewoods. The Capercaillie is not renowned for seeking
attention, it is instead a more shy and retreating bird.
It can be seen during the lekking season from hides at RSPB Abernethy Forest, Loch Garten reserve. Capercaillie are shy birds and do not react well to disturbance by people, vehicles or domestic animals, such as dogs. See our section on responsible access for more information.
Types of food
Berries, Shoots, Stems and Insects (Hatchlings). The
Capercaillie is a highly specialised herbivore. During the
summer the Capercaillie feeds mainly on blaeberry leaves and
berries as well as some shoots and seeds. It grazes on the
ground during the summer period. The young Capercaillie, in
their initial few weeks of life are highly dependent on a protein
rich diet, and therefore feed mainly on insects associated with
the blaeberry plant. The quantity of insects is determined
greatly by the weather conditions of the spring and early summer -
If there spring and early summer is wet and cold, there are often
fewer insects and an increased rate of young mortality.
However, if the spring and early summer are warm and dry, the
quantity of insects will be sufficient to allow for fast growth of
the young. During the winter months the Capercaillie will
adopt a primarily arboreal lifestyle, feeding mainly on conifer
needles and buds.
Sounds and calls
During lekking the male Capercaillie's call sounds like a series of 'clicks' and 'pops'. This call can carry for several
kilometres and is used to attract females. Much of the
Capercaillie's call is thought to be out with the human hearing range.
Hear the song of the Capercaillie
(mp3 format approx. 1Mb)
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