This publication is the fourth, major ‘world bird checklist’ for the non-passerines published in the last few years. Three of them already also include the passerines - Gill & Donsker (2014), Clements et al. (2014) both of which are regularly updated online, and Dickinson & Christidis (2014), while the publishers of this new HBW / BirdLife checklist state that its passerine volume will be published in early 2016.
The first questions therefore must be ‘Do we need another checklist?’ and ‘How do they compare?’ The HBW / BirdLife book is certainly very different, most obviously in that it is considerably larger and that is largely because it contains so much more. The others are all essentially just lists of species and subspecies, albeit with notes and sources noted. This one includes a full list (obviously!), but there are also illustrations and small distribution maps for all species, as well as rather more details of the reasons for their taxonomic decisions.
Previous checklists have usually been based on the Biological Species Concept (BSC) or Phylogenetic Species Concept (PSC). This one is different, albeit stated to be rooted in BSC. In 2010, a paper was published in Ibis (Tobias et al. 2010) describing a method of objectively determining the ‘distance’ between forms. This is based on a scoring system using plumage characters, measurements, ecology, vocalisations and geographical distribution; then, if a pair of forms differs by a score of seven or more they are deemed to be different species. Slightly controversially, the system does not include genetic distances, in part because all groups have yet to be so investigated. The scoring system has been used throughout this new list for species determination and for the considerable majority of taxa it merely restates traditional divisions. However, the delimiting and determination of races has not been subjected to quite the same objectivity and rigour, retaining a fair amount of subjectivity, although here too the majority of decisions do follow tradition. A full explanation of the entire system is included in the lengthy introductory chapter, which should be deemed compulsory reading for all taxonomists, although they will not necessarily agree with it.
So how does the taxonomy actually compare to other lists? For the purposes of this review, I have only considered species that occur in the area covered by ABC. Overall, the book considers there to be 1,189 extant species in the ABC region. This compares with 1,183 in the IOC list (version 4.3 published July 2014), 1,154 in the Clements list (version 6.9 published August 2014) and 1,134 in the latest ‘Howard & Moore’ list (Dickinson & Remsen 2013). But, although the total number here is very similar to the IOC list, those forms considered to be species are by no means the same - and if you sum all taxa treated as species by at least one of the four checklists, the total would be 1,210! To take this a little further, this new list has lumped 27 forms considered by IOC to be species into others, the majority also lumped by one or both of the other two. But, it also splits 33 new species and it seems that barbets are especially favoured with ten extra species. There are also a few different decisions as to which groups should be treated at family level. For example, the HBW / BirdLife list retains the flufftails Sarothrura spp. within the rails (Rallidae), but splits some of the storm petrels (Hydrobatidae) into a new family Oceanitidae, both contrary to the IOC list yet coincident with the Howard & Moore list.
The considerable majority of genera and families here agree with other lists, although there are some new ones. For example, several of the ‘teal’ and ‘shoveler’ ducks are now placed within Spatula not Anas, and several Lybius barbets are now in Pogonornis, but it should be noted that Howard and Moore often uses these ‘new’ names too. Needless to say, the detail of the order of species in families and of families overall is initially idiosyncratic, and it is certainly different in several respects from all other lists. The index is therefore essential, especially to find the smaller families and monotypic genera within large families, and sometimes readers will need to search for the specific name, rather than that of the genus, as the latter has changed from the former status quo.
Does this splitting of species and redefining what constitutes a species matter? In many ways no, although for those interested in their life lists, it necessitates stating which taxonomy you are following. However, in conservation terms, these days it probably does matter rather more. In some parts of the world a ‘species’ is enshrined in law as an entity to be conserved, whereas subspecies do not possess anything like as much ‘clout’. For non-scientists too, a species represents a more easily understandable entity, and such people certainly do not work with the uncertainties, arguments and differences that are the professional playground of taxonomists. Whether this was a reason for BirdLife International to collaborate with and endorse this new list that recognises more species is unknown, but previous versions of BirdLife’s checklist were rather more conservative than most others.
The book itself is impressive and large. The introduction is comprehensive and fully explains the rationale behind the methods and explains the symbols used. Then there is the list itself, with text and plates facing each other, and the maps placed next to the relevant illustrations. Most of the images are taken from the earlier volumes of Handbook of the Birds of the World, although there are many revised and new depictions, the latter mainly to accommodate the new species, but all have been completely rearranged onto new plates to take account of the revised order. The maps too have been updated from the originals as necessary, but are otherwise similar to those in the earlier volumes. The texts are headed by the accepted scientific and English names, while French, German, Spanish and sometimes alternative English names are also included. The main paragraph essentially reproduces the taxonomic section of the species accounts from previous volumes of HBW, although there is usually rather more explanation and documentation of the decisions adopted. The list of accepted subspecies with bibliographic references and brief notes of range follow, again very much on the lines of the original HBW, although completely updated and revised. The book is completed by two appendices of extinct forms (one with illustrations and one without), an appendix of reference maps noting place names to province level, a comprehensive bibliography (with full references) and a full index. All thesemake for a highly appealing book.
Would I buy it? There is no question that it is the most attractive of the four main world checklists, but it is also the most expensive (retailing at a similar price to the two volumes of Howard & Moore, whereas the IOC and Clements lists are free online). Take your choice and, if this book is it, await the passerines volume with interest.