Actress Kirsty Oswald has embarked on an ambitious bird-watching feat; over the course of a year, she plans to spot 100 different species of bird in the British Isles. In this episode of Tweet of the Day, she explains how a serendipitous walk led to her undertaking such a task, and how enthusiasm, enjoyment and a love of walking can be more fortuitous than formal ornithological knowledge. Producer: Elliott Prince