Biology
Tetrao urogallus © Lomvi, Creative Commons Attribution-Share Alike 3.0 Unported
Male and female capercaillie can be discriminated easily by their size and colouration.
The male:
- is bigger than the female
- weighs approximately 4.3 kg
- is about 74 cm in length
- has a wingspan of 1.06m
- is predominantly black in colour
The female:
- is much smaller
- weighs about half as much as the male
- is a reddish brown colour
Adult birds feed on blaeberry from early spring through to summer, as well as:
- plant buds
- pollen cones
- flowers
- seeds
- conifer needles are eaten primarily in winter
Chicks initially feed on invertebrates, particularly caterpillars - this supplementary protein in the diet is important for their early development.
Lekking
The capercaillie is well known for the strange clicking, gulping and saw whetting calls that males make when they display at clearings in the woods known as leks. The ritual itself is known as lekking.
In spring from April to mid-May, males (cocks) gather at leks to strut and posture, fanning their tails and making their strange calls to maintain their status with other cocks. Sometimes, these displays become ferocious fights that can result in injury.
The females (hens) visit the leks and mate with their chosen male. They then nest and rear the young with no help from the male.
The nest scrape is hidden in the heather or among the roots of a tree where the hen lays 5–12 eggs on the ground with incubation taking from 26 to 29 days. Young capercaillie leave the nest within a day of hatching, although the adult female continues to offer them shelter from the weather and protection against predators throughout the summer until they fledge in late August.