These natural history studies relate to the series of drawings that Turner executed for his most important patron, Walter Fawkes of Farnley Hall, which were originally part of the five volume album entitled the Ornithological Collection compiled for the library at Farnley. Turner's drawings were subsequently removed on the instructions of John Ruskin and mounted in a separate album called the Book of Birds, which was sold in 1985 to Leeds City Art Gallery. Other examples of Turner's natural history studies are in the Turner Bequest, TBCCLXII/358 and 359.
The only section of The History of British Birds, not covered in the Ornithological Collection was the second third of 'Water Birds', possibly because examples of feathers (which were bound with the illustrations) were difficult to come by. It would appear that the heads of the smew and merganser were intended for this section. The Guinea Fowl duplicates a subject in the Ornithological Collection and was probably copied by Turner for Amelia Hawkesworth, younger daughter of Walter Fawkes's younger brother Francis Ramsden Hawkesworth (1774-1824/5).
Ruskin prized these natural history studies very highly. Writing to his father in 1852 after the death of Turner about works he wished to acquire, he described the Natural History studies of Walter Fawkes as 'those which I would give any price for if I had it to give' and of the drawings in the Turner Bequest he wrote 'these bird drawings of Turner were more utterly inimitable than... anything else he had done.'
For further information see A. Lyles, Turner and Natural History, The Farnley Project, Tate Gallery, exhibition catalogue, 1988.