Early scientific works on birds, such as those of Conrad Gessner, Ulisse Aldrovandi and Pierre Belon, relied for much of their content on the authority of the Ancient Greek philosopher Aristotle and the teachings of the church,[2][3] and included much extraneous material relating to the species, such as proverbs, references in history and literature, or its use as an emblem.

[11] The commercial success of the Ornithology is unknown, but it was historically significant,[12] influencing writers including René Réaumur, Mathurin Jacques Brisson, Georges Cuvier and Carl Linnaeus in compiling their own works.

[15] When he was researching published sources for his bird project, Bewick relied particularly on Edwards' book and the multi-volume Histoire Naturelle of the French naturalist Georges-Louis Leclerc, Comte de Buffon.

[24] Bewick became well known for his engravings, including the woodcuts for Oliver Goldsmith's Traveller and The Deserted Village, for Thomas Parnell's Hermit, and for William Somervile's Chase.

[28][29] The preface to A History of British Birds states that "while one of the editors [Bewick] of this work was engaged in preparing the cuts, which are faithfully drawn from Nature, and engraved upon wood, the compilation of the descriptions .. (of the Land Birds) was undertaken by the other [Beilby],[30] subject, however, to the corrections of his friend, whose habits had led him to a more intimate acquaintance with this branch of Natural History", and goes on to mention that the compilation of text was the "production of those hours which could be spared from a laborious employment", namely the long hours of work engraving the minutely detailed wood printing blocks.

Bewick then describes the bird, typically in one paragraph, naming any notable features such as the colour of the eyes ("irides"), the bill, the legs, and plumage on each part of the body.

Bewick then mentions any other facts of interest about the bird; in the case of the musk duck, this concerns its "musky smell, which arises from the liquor secreted in the glands on the rump".

The musk duck is stated to have been drawn from a "living specimen" which was however "excepting the head, entirely white", unlike the "general appearance" shown in the woodcut; the bird "was lent to this work by William Losh, Esq., of Point Pleasant, near Newcastle".

"[b] In A Memoir (posthumously published in 1862), Bewick states that he intended to "stick to nature as closely as I could", but admits that he had "in several cases" to rely on the stuffed "preserved skins" of his neighbour Richard Routledge Wingate.

[c] The first volume "containing the History and Description of Land Birds" begins with a preface, an introduction, and a list of technical terms illustrated with Bewick's woodcuts.

The introduction begins: In no part of the animal creation are the wisdom, the goodness, and the bounty of Providence displayed in a more lively manner than in the structure, formation, and various endowments of the feathered tribes.The birds are divided into granivorous (grain eating) and carnivorous groups, which are explained in some detail.

The speed, senses, flight, migration, pairing behaviour and feeding of birds are then discussed, with observations from Spallanzani and Gilbert White, whose Natural History and Antiquities of Selborne was published in 1789.

[45]Bewick also mentions conservation, in the context of the probable local extinction of a valuable resource: "Both this and the Great Bustard are excellent eating, and would well repay the trouble of domestication; indeed, it seems surprising, that we should suffer these fine birds to be in danger of total extinction,[d] although, if properly cultivated, they might afford as excellent a repast as our own domestic poultry, or even as the Turkey, for which we are indebted to distant countries.

Bewick discusses the question of where many seabirds go to breed, revisits the subject of migration, and concludes with reflections on "an all-wise Providence" as shown in Nature.

[48] In 1805, the British Critic wrote that it was "superfluous to expatiate much on the merits of a work" that everyone liked because of "the aptness of its descriptions, the accuracy of its figures, the spirit of its wood engravings, and the ingenious variety of its vignettes.

"[52] John Brewer, writing in the London Review of Books, says that for his Birds, "Bewick had acquired national renown as the artist who most truthfully depicted the flora and fauna of the British countryside."

His engravings of British birds, which represent his work at its finest, are almost all rendered with the precision of the ornithologist: but they also portray the animals in their natural habitat – the grouse shelters in his covert, the green woodpecker perches on a gnarled branch, waders strut by streams ..." He observes that "Most of the best engravings include a figure, incident or building which draws the viewer's eye beyond and behind the animal profile in the foreground.

More directly, the review notes that "Bewick was aware that his role was to offer a modest guide to birds that the common man not only could afford but would also want to possess."

The History of British Birds (2 vols, Newcastle upon Tyne, 1797–1804) reveals Bewick's gifts as a naturalist as well as an engraver (the artist was responsible for the text as well as the illustrations in the second volume)."

The article notes that the book makes "extensive use of narrative tailpieces: vignettes in which manifold aspects of north-country life are expressed with affection, humour and a genuine love of nature.

"[43] Dissenting from the general tone of praise for Bewick, Jacob Kainen cites claims that "many of the best tailpieces in the History of British birds were drawn by Robert Johnson", and that "the greater number of those contained in the second volume were engraved by Clennell.

Granted that the outlook and the engraving style were Bewick's, and that these were notable contributions, the fact that the results were so close to his own points more to an effective method of illustration than to the outpourings of genius."

"[56] Jenny Uglow, writing in The Guardian, notes that "An added delight was the way he filled the blank spaces with 'tail-pieces', tiny, witty, vivid scenes of ordinary life."

She describes the importance of Birds in Jane Eyre, and ends "He worked with precision and insight, in a way that we associate with poets such as Clare and Wordsworth, Gerard Manley Hopkins and Elizabeth Bishop.

[61][f] In M. R. James' short story, Casting the Runes, a Bewick print is also referenced, described as "a moonlit road and a man walking along it, followed by an awful demon creature.

"[62] The English romantic poet William Wordsworth began his 1800 poem The Two Thieves; or, the Last Stage of Avarice with the lines[63][64] Oh now that the genius of Bewick were mine And the skill which he learned on the banks of the Tyne.

[63] Peter Hall's 1974 film Akenfield (from the 1969 book by Ronald Blythe) contains a scene where the grandfather as a young man is reaping a cornfield.

[65] The advent of mechanical printing techniques from the 1860s led to something of a decline in his importance,[65] but his fame, already nationwide across Britain for his Birds, grew during the nineteenth century.

[73] In 1821 a new edition appeared with supplements to both volumes and additional figures, with the imprint "Printed by Edward Walker, Pilgrim-Street, for T. Bewick: sold by him, and E. Charnley, Newcastle; and Longman and co., London, 1821."