In 1927, with his first wife Doris Shellard, he took a 21-year lease of Skokholm, a small island some four miles off the western tip of Pembrokeshire, which was inhabited only by rabbits and seabirds. Attempts to make a living from catching and selling rabbits and breeding chinchilla rabbits were abandoned when he found he could make a better living writing articles and books. He began to study migratory birds from 1928, establishing the first British bird observatory in 1933, and carrying out extensive pioneering research on breeding Manx shearwaters, Atlantic puffins and European storm-petrels. He was encouraged to record the exact incubation and fledging period of the Manx shearwater by Harry Witherby, the then editor of British Birds. He provided the initial catalyst for the entire British Bird Observatory movement which, following the war-time interruption, reached its zenith in the fifties. He described his research in several books, including Dream Island, Island Days and I Know an Island. The work brought him to the notice of a wider circle of conservationists and naturalists, among them Peter Scott and Julian Huxley. Lockley's notable scientific monograph Shearwaters is a result of a twelve years' study. He founded the Pembrokeshire Bird Protection Society which later became the West Wales Field Society. He urged the broadening of the activities of the original Society and the extension of its area to include the whole of West Wales and it was at his insistence that the West Wales Field Society was incorporated as the West Wales Naturalists' Trust. With Julian Huxley he made one of the first professional nature films, The Private Life of the Gannets, which won an Oscar.
Post war
Lockley continued farming on the mainland when Skokholm was used by the military during the Second World War. He played a key part in the preliminary survey of the natural history of Skomer Island in 1946, re-establishing Skokholm as a bird observatory and establishing the Council for the Promotion of Field Studies in Dale Fort. He played a leading role in setting up the Pembrokeshire Coast National Park in 1952, and in mapping out the coastal footpath around the county. Living at Orielton, a large estate near Pembroke, he undertook an intensive four-year scientific study of rabbit behaviour for the British Nature Conservancy during the 1950s. As chairman of the West Wales Field Society, he also led an unsuccessful campaign against the building of a large oil refinery at Milford Haven. His belief that successive British governments were not sufficiently aware of the threat to the landscape from industrial development led to his decision to emigrate to New Zealand in 1970, with his third wife. There he continued to write, mostly about islands and birds, but also novels, and to travel among the islands of Polynesia and in the Antarctic. Lockley was awarded an Honorary MSc by the University of Wales in 1977, in recognition of his distinction as a naturalist. In 1993 he was awarded the Union Medal of the British Ornithologists Union. He died in 2000, aged 96. His ashes were scattered from the boat Dale Princess, in the waters just off Skokholm Island in 2000.
Lockley's The Private Life of the Rabbit played an important role in the plot development of his friend Richard Adams's children's book Watership Down. The New York Times obituary observed "It was a rigorously factual work with none of the anthropomorphic sentimentality that infused Watership with its charm, but it bristled with insights." With Lockley's permission, Adams introduced him as a character in his later novel The Plague Dogs.
