In April, the male capercaillies move to an open part of their woodland territory and perform their ‘lek’. Lek is an Old Norse word meaning ‘to dance’, and relates to the birds’ bizarre courtship display. The males strut about with their tails fanned out, and wings held down, while producing an extraordinary sequence of noises including some that sound like strangled gurgles and asthmatic wheezes. Interspersed with these are popping noises like corks being drawn from champagne bottles. Some experts believe that some of these sounds, below the range of human ears, carry for many miles and declare to any female capercaillie that the male making the noise is in his prime. They may also indicate that he has a fine territory, well provided with nesting sites and a good food source for the chicks. As the females arrive at the lekking site, the males become even more excited. Sometimes, several males will gather at a lekking site and spectacular fights can break out, during which birds can be seriously injured and even killed.
Once the female has been mated, the males play no further part in rearing the young. Between 5 and 12 eggs is the usual clutch, but as many as 18 have been recorded. They are laid in a nest on the ground, lined with pieces of nearby vegetation. Incubation takes from 26 to 29 days and the young chicks, like those of all game birds, are highly mobile, leaving the nest with the female the day after they hatch. Their wing feathers appear in two weeks and the young birds are then able to fly, albeit rather weakly. They stay as a family throughout the rest of the summer months, joining larger groups of birds in the autumn.
Capercaillie feed on blaeberries (also known as bilberries), shoots and seeds. In common with many birds, the chicks are fed initially on insects, graduating to the more vegetable-based adult diet later.