Newton's interest in extinct bird species such as the dodo, great auk and great bustard led him to work towards the protection of birds. He influenced the legislation of the Sea Birds Preservation Act 1869. Newton was a prominent supporter and member of the Society for the Protection of Birds (later, 1903, the RSPB) from its inception in 1889, and carried on a long campaign to influence women against the fashion of adorning their hats with the flight feathers of raptors and other fine birds. His letters to "The Times" and addresses to the British Association for the Advancement of Science meetings on this subject were regularly reprinted as pamphlets by the Society. Newton determined that extinction cause by human actions was different from extinction resulting from natural processes including evolution. He made efforts to clarify that his motivations for conservation were scientific and that these were distinct from sentiments influenced by earlier movements against animal cruelty and vivisection.