The most famous experiments on the peppered moth were carried out by Bernard Kettlewell under the supervision of E.B. Ford. In one of Kettlewell's experiments, moths were released into a large (18 m by 6 m) aviary, where they were fed on by Great Tits ("Parus major"). In 1953, Kettlewell experimented at Cadbury Nature Reserve in Birmingham. He marked, released and recaptured the marked moths. He found, in polluted woodland, more "typica" morphs were taken. This showed that the melanistic phenotype was important to the survival of peppered moths in such a habitat. Kettlewell repeated the experiment in 1955 in an unpolluted woodland in Dorset, and again in polluted woods in Birmingham. He was accompanied by Niko Tinbergen, and they made a film of this. Further studies by others found similar results. Finally, in 1996, work on both sides of the Atlantic found a correlation between changes in melanic frequencies and pollution levels.