Northern rockhopper penguin been caused by a vicariant event caused by a shift in the position of the Subtropical Front during the mid-Pleistocene climate transition. Analysis of a part of a mitochondrial control region from a northern rockhopper penguin found on the Kerguelen Islands showed that it may have come from Gough Island, 6,000 km away, and that the southern and northern rockhoppers are genetically separate, though some individuals may disperse from their breeding colonies. Many taxonomists have yet to recognize the split, although some are beginning to do so. More than 99% of northern rockhoppers breed on Tristan da Cunha and Gough
Free as a Bird Beatles songs, such as "Penny Lane", "Paperback Writer", "A Day in the Life", "Eleanor Rigby", "Helter Skelter", "Piggies", "The Continuing Story of Bungalow Bill", "Strawberry Fields Forever", "Doctor Robert", and "The Fool on The Hill". Between 80 and 100 allusions to the Beatles' story, music and lyrics in the video have been estimated. Although the bird can be heard at the beginning of the video, it is never seen. Neil Aspinall (Apple Records executive at the time) said that this was because no-one could agree on what kind of bird it should be. Pytka had to send his ideas to