British Birds 107, November 2014, pp.706-707

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HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 1. Non-Passeriformes

By Josep del Hoyo, Nigel J. Collar, David A. Christie, Andrew Elliott and Lincoln D. C. Fishpool Lynx Edicions, 2014 Hbk, 904pp; many photographs, 357 colour plates, distribution and reference maps ISBN 978-84-96553-94-1 Subbuteo code M24238 £151.00 BB Bookshop price £135.00

 

Following the pattern established by the multivolume BWP, the magnificent Handbook of the Birds of the World (HBW) completed its publication in 17 volumes, transferred into a digital format and is now moving on to a two-volume ‘HBW Concise’, in the form of a world checklist. The first volume (covering the non-passerines) has just appeared; the second, on the passerines, is due in 2016. The present book is the same size as an original HBW volume, mainly because it is the first world checklist also to illustrate and map every known species.

The Checklist is laid out in attractive doublepage spreads with text on one side facing corres - ponding illustrations on the other. The text is extracted from the HBW species accounts, with appropriate revision. Each species header gives the scientific and English names, together with conservation status and a link to the relevant HBW volume and page. If taxonomy or nomenclature has altered since HBW, the earlier name is also given, a convenient signposting to these changes. The body of the account includes French, German, Spanish and significant alternative English names, taxonomic notes, and a list of recognised subspecies with their authors, dates and distribution. The taxonomic notes include the original scientific name applied to the taxon (omitted from many other regional or world checklists), its author, date and type locality, and further details on taxonomy and nomenclature.

The listed species and the most distinctive subspecies are all illustrated, mainly with reduced images from HBW, among which 783 have been ‘improved’ and 242 have been added. For example, the herons on p. 405 include new illustrations of Ardea cinerea monicae, A. purpurea bournei, as well as A. alba modesta, A. a. melanorhynchos and A. a. egretta. Unfortunately, many of the white herons and egrets (and some other white birds) are grey and dull here but, those apart, the colour reproduction does not differ greatly from HBW. The Checklist is not intended to be an identification guide and the illustrated birds are all adults in breeding plumage, with females shown only when the sexes are noticeably different. There are no juveniles, non-breeding plumages or birds in flight apart from the swifts, petrels and a few others. The paintings are of a uniformly high standard and, while the smaller size has made them marginally less impressive than in HBW, the Kagu Rhynochetos jubatus on p. 155 has become quite exceptional. The plates include a scale bar, updated distribution maps for every species, and English as well as scientific names (only scientific names were given in HBW, leading to much page turning). There are 34 pages of reference maps and two appendices of extinct species (which would surely have been better in one).

More compromises will have to be made before a consensus over English bird names is achieved. The Checklist uses names based on HBW and BirdLife’s own lists and most will be widely recognised. The latter has a stated preference for avoiding eponyms where possible although thankfully there are still many exceptions: for example, Larus ichthyaetus is called Pallas’s Gull rather than Great Black-headed Gull.

While the authority of the text, the quality of the plates and the revised distribution mapping for every species are more than enough to establish this as an exceptional volume, it is the authors’ approach to species-level taxonomy that they believe is the most distinctive feature of the book. The number of recognised species is increasing year by year, in large part through the elevation of forms previously treated as subspecies following reassessment of characters, new information on vocalisations, distribution, ecology or DNA, and from the changing approaches used to delimit species. The process of re-evaluating candidate taxa has generally not kept up with the flood of new data and this has at times hindered effective conservation. In a major exercise, the authors have carried out a massive sweep using new criteria, adding a total of 462 species since HBW, about half of which were proposed by other authors after the publication of the relevant volumes. The criteria used here were published by Tobias et al. (Ibis 152: 724–746) and they are carefully explained in the introduction. The Tobias procedure is established on Biological Species Concept foundations but applies numerical scores to differences between taxa; a score of seven or more is taken to indicate separate species. Scores for biometric and vocal differences are derived from means and standard deviations and presented as Cohen’s d statistic. Plumage differences are scored through a subjective four-point scale. Ecology, behaviour and distributional data are weighted differently. The authors illustrate their complicated procedure through numerous worked examples and the species texts include many of the scores for their newly elevated species.

 The Tobias criteria were introduced originally because the authors found existing methods of delimiting species to be subjective and inconsistent. Creditably, they openly draw attention to areas where their own criteria have run into the sand. They quote an example, Charadrius dealbatus, where other researchers independently calculated Tobias scores. Out of 15 characters assessed by one or both teams, they examined five in common and the scores for only two of these agreed – hardly a ringing endorsement. They also concede that some similar taxa (e.g. Larus argentatus/ smithsonianus, Gallinago gallinago/delicata, Pterodroma feae/deserta) failed to meet the threshold of seven, yet they accepted the splits. Similarly, Hydrobates castro/H. monteiroi defeated their methodology. It is reported that Caprimulgus meesi is phenotypically indistinguishable from C. macrurus schlegelii (although the illustrations appear to show remarkably different birds), but the split is adopted on vocal criteria, which fall far short of their threshold. In the case of Puffinus assimilis/P. lherminieri and the albatrosses, they completely abandoned all attempts to apply their criteria and have simply followed published recommendations.

The authors have certainly performed a great service in their review of species but, as illustrated by the above examples, it serves to highlight that no known system can definitively identify which taxa deserve to be treated as species. There are theoretical problems with the Tobias procedure (not discussed here) and I question whether its criteria and complexity produce better or more consistent results than other methods. It brings to mind the abandoned numerical taxonomy of the 1970s, and the Tobias scheme’s failure to integrate DNA data reinforces a detachment from modern science.

Higher taxonomic levels are beautifully illustrated on the dust jacket but are not discussed, being drawn from an as yet unpublished book by Winkler et al. (Bird Families of the World). Genera have been revised from HBW, though I noticed, for example, that Bonasa and Tetrastes are treated under the former name despite abundant contrary evidence and one of their cited references stating explicitly that genetic data do not support monophyly of this grouping.

This is the second major world checklist to appear within the last 12 months, following The Howard & Moore Complete Checklist of the Birds of the World, 4th edn, Vol. 1, also to be completed with a passerine volume. The HBW Checklist contains 4,417 non-passerine species against H&M’s 4,072. Both books are impressive, scholarly additions to the literature containing much original information but, regardless of the idiosyncratic species delimitation, this HBW Checklist is clearly in a class of its own. Having a full checklist of all the non-passerine species and subspecies, together with illustrations and maps in one remarkable volume, simply cannot be beaten. However, checklists go out of date quickly and it remains to be seen whether potential purchasers will prefer the hard copy or the regularly updated online HBW Alive (Brit. Birds 107: 490–491).

Alan Knox