Prestt was a professional scientist with a passion for birds, not least for sparrowhawks and herons, and also for snakes, some of his earlier research being with adders on the Dorset heaths, whose scales he tampered with delicately so as to recognise individuals. By the accidental good fortune which moulds most successful careers, he developed a happy sequence gathering strength for the main task to come, as Director General of the Royal Society for the Protection of Birds.
Appointed by the great Max Nicholson, doyen of international conservationists and then head of the Nature Conservancy, as "his ornithologist" in 1959, Prestt found himself involved in a cause celebre of the Sixties. Rachel Carson's Silent Spring (1963) had ignited the bombshell of specific pesticide residues causing environmental disaster. It was Prestt's first important job at the Monks Wood Experimental Station to be part of the team teasing out the relationships between ingested chlorinated hydrocarbons and the thin shells of birds' eggs, leading to recognition of the threats to food chains and to humans.
Later he went to the Cabinet Office and to the Department of the Environment, under Peter Walker, to wrestle with the pollution problems which are part of the roots of the Environment Bill which was still meandering through the House of Lords on the day that Prestt died. Later still he moved to become deputy head of what had become the Nature Conservancy Council.
In 1975, he received an unexpected telephone call in his office at the NCC inviting him to dine. His hosts were the chairman of the council and committees, four in all, of the RSPB. Eschewing head-hunters, they had decided that Prestt must be their man. And so it was. For 19 years, as Director General and ultimately as President, Prestt's combination of enthusiasm, goodwill and solid decency allied to shrewd skills was an important component in the society's rocketing growth to a membership of 800,000 and a reserves estate of some 150,000 acres. He became a talisman for the RSPB in all that it aspired to achieve for bird conservation. And not only for the society; he became involved with international affairs and played a leading part in bringing the message of protecting birds and their habitats to countries overseas.
But Prestt is likely to be best remembered by those closest to him not for what he did but for what he was. At 65 he still had more than a hint of a mischievous schoolboy about him. And he had one of those infectious smiles that start slowly and then burgeon: at no time better than when, on a summer's dusk in a remote Sutherland bog, his companion having become hoarse trying for hours to coax a corncrake to call back, there it was - his first ever. He was a splendid and wicked mimic, in the nicest possible way. Many a car journey to reserves became a joyous affair as the tones of respected ornithologists and politicians reverberated, thanks to the Prestt magic. His eagerly sought tour de force was a fierce argument between two senior bird men at a Balkans roadside as to the identity of a black spot in the sky.
Life was not, however, all plain sailing. He and his wife, Ann, lost one of their beloved children in a car accident, and Ian found some aspects of managing a large staff irksome and far removed from seeing to the immediate needs of avocets and bitterns.
Ian Prestt, ornithologist: born 26 June 1929; Assistant Regional Officer (SW England), Nature Conservancy 1956-59, Assistant to Director General and Ornithological Officer 1959-61, Deputy Regional Officer (N England) 1961-63; PSO, Monks Wood ExperimentalStation 1963-70; Deputy Director, Central Unit on Environmental Pollution , Cabinet Office and Department of Environment 1970-74; Deputy Director, Nature Conservancy Council 1974-75; Director, Director General, Royal Society for the Protection of Birds 1975-91, President 1991-95; CBE 1986; married 1956 Ann Wagstaffe (two daughters, and one son deceased); died 24 January 1995.