Boka omfatter de opprinnelige kunstverk fra HBW serien, så vel som flere hundre nye illustrasjoner, alt i to kompakte volum.
In this Checklist, a modern, broad version of the Biological Species Concept (BSC) has been applied, with the aid of the scoring system to evaluate differences in morphology, vocalizations, ecology and geographical relationships published in Ibis by Tobias et al. (2010)*. For the non-passerines, this has resulted in relatively few lumps (21) but a much higher number of splits, 461 in total at the time of writing, compared with the taxonomy presented in the HBW series. Groups with major changes in species numbers include:
* J.A. Tobias, N. Seddon, C.N. Spottiswoode, J.D. Pilgrim, L.D.C. Fishpool & N.J. Collar (2010). Quantitative criteria for species delimitation. Ibis. 152: 724–746.
An extensive introduction, with many illustrated examples, explains the rationale and advantages of the taxonomic system adopted in the Checklist, as well as how to use the book.
Two appendices cover all the species considered to have become extinct since 1500. The first gives full treatment, including text, illustration and former range map, for the extinct species known from complete specimens. The second provides information for the extinct species not known from complete specimens.