In 1674 and the following year, he was busily engaged in the task of preparing for the press Mr Willughby's observations on birds. These notices had been committed to paper without any method, and left in a very imperfect state, so that the trouble of revising and digesting was of no light kind. Without at all detracting from the merits of the author, whose labours, according to Dr Derham, were such, "that he allowed himself little or no time for those recreations and diversions which men of his estate and degree are apt to spend too much of their time in, but prosecuted his design with as great application, as if he had been to get his bread thereby," it may fairly be presumed, and indeed has been generally admitted, that the greater part of his works belong in fact to Mr Ray, who, however, claimed no merit in the performance. The book was published in 1676, in Latin, with engravings, which, in the titlepage, are designated as _icones elegantissimi et vivarum avium simillimi_, although few who inspect them will be disposed to concur in the opinion now stated. It was afterwards translated into English by his affectionate editor, and put forth with large additions in the year 1678. Derham apologizes for the inferior execution of the plates, which were done at the charge of the author's widow. "Considering," says the Doctor, "how well the engravers were paid for their labour, it is great pity they had not had some able person in London to have supervised them, that they might have given better likenesses to the birds than what most of them have. But this is what Mr Ray could only complain of, but not help, by reason of his being in Warwickshire, at a distance from London, where every thing was transacted by letters,--a method which could never afford sufficient directions in a matter of that nature." The descriptions, however, are in general excellent, regard being had to the state of science at the time when they were written. Some of them, indeed, are very imperfect, and there is, besides, a deficiency of method, which becomes more striking when they are compared with those of Temminck or Selby, or any other of our best modern ornithologists. In this important work birds are divided into _Terrestrial_ and _Aquatic_. The former are disposed in the following order:-- In the first place, land-birds are either furnished with hooked-bill and claws, or have these organs nearly straight. Those with hooked-bill are carnivorous and predatory or frugivorous. The former are either diurnal, that is, hunt by day, or nocturnal, seeking their food by night. The diurnal carnivorous birds are either large, as the _eagles_ and _vultures_, or small. Of the former there are two kinds, the _generous_, as the peregrine falcon, lanner, goshawk, &c.; and the _ignoble_, as the _buzzard_, kite, &c. The smaller predatory birds are the _shrikes_, and birds of paradise. The nocturnal birds of prey are the _owls_.