The capercaillie, Gaelic for ‘great cock of the wood’, is the largest bird in the grouse family, with the turkey-sized males weighing up to 11lbs (5kg). In March, cocks begin contesting for the best breeding territory, known as a lek, before mating begins properly later in the season. Beak held aloft, huge black tail fanned out and throat feathers bristling, it patrols the area, emitting a creaky call, followed by a succession of clicks and a final ‘pop’, like a cork from a bottle. In Britain, it is found exclusively in the pinewoods of the Highlands, with the majority in the Cairngorms National Park. At this time of year, the birds, which are critically endangered in the UK and very difficult to spot, are extremely sensitive to disturbance. The lek, therefore, is almost impossible to see, and the sites are often protected from human interference.