Capercaillie (Tetrao urogallus) male displaying in pine forest in snow, Cairngorms NP, Highlands, Scotland, UK, January. Photographer quote: 'The capercaillie is Britain's fastest declining bird and restricted to the pine forests of northern Scotland. It's the ultimate bird in my opinion.' Did you know? The capercaillie is a resident of Scotland’s northern forests and is the world’s largest grouse.