 By 1963 an international organisation founded with the goal of protecting Doñana had purchased 7 @,@ 000 hectares ( 17 @,@ 000 acres ) in the area . After winning their fight against the construction plans González @-@ Gordon , Bernis and Valverde wished to create a Spanish foundation for ornithology . The idea to start the organisation had already come up in their first meeting . In May 1954 they founded the Spanish Ornithological Society ( SEO ) in Madrid , which currently is the Spanish affiliate of BirdLife International . The trio had written the founding statutes among themselves . The organisation was supported by visits to Doñana of famous ornithologists as Edward Max Nicholson and Julian Huxley , with González @-@ Gordon guiding them around . He would also serve as chair of the board of SEO between 1966 and 1968 . The Doñana area was turned into Doñana National Park in 1969 . The González @-@ Gordon family ceded much of its land between Bonanza and <unk> for the creation of the national park . In 1994 the area was turned into an UNESCO World Heritage Site and currently measures 543 square kilometres ( 210 sq mi ) . The park has a wide range of ecosystems and is especially important for migratory birds . González @-@ Gordon also wrote a translation of Roger Tory Peterson 's A Field Guide to the Birds of Britain and Europe in 1957 . 
