The first part of a landmark new series about the wildlife of the Scottish Highlands, narrated by Ewan McGregor. It's late March in the Cairngorm mountains and the hills are on fire! Old heather is being burned in readiness for the grouse season. Traditionally, this inferno marks the end of winter and the start of spring in this wilderness. But spring is the most unpredictable of all seasons here. Ospreys, red squirrels, dippers, capercaillies, roe deer and bottlenose dolphins have struggled to find food and raise their young while coping with the extremes of wind and weather.

• Ewan McGregor