London dealer Michael Tollemache, whose winning bid came in more than £1.3m above the £6m estimate, described the work as "priceless".

The four-volume work, from the private collection of Frederick, 2nd Lord Hesketh, comprises 435 hand-coloured etched plates with line-engraving and aquatint.

The engravings were created by Robert Havell and Son, of London, and WH Lizars, of Edinburgh, from the original life-size watercolours by John James Audubon.

All prints were reproduced in double-elephant folio, which represents a sheet size of around 972mm x 654mm, from the copper plate etchings and then hand coloured.

The Birds of America took Audubon 12 years to complete and his technique involved shooting the birds before mounting them with wire in order to pose them for his sketches.

See PrintWeek associate editor Jo Francis' blog, musings on the enduring beauty of books.