British Birds 110, June 2017, pp.358-359

British Birds 110 · June 2017·358-361

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HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines

By Josep del Hoyo, Nigel J. Collar, David A. Christie, Andrew Elliott, Lincoln D. C. Fishpool, Peter Boesman and Guy M. Kirwan

Lynx Edicions, 2016

Hbk, 1,013pp; 446 colour plates, distribution and reference maps

ISBN 978-84-96553-98-9, £205.00

The first volume of this monumental work was reviewed in 2014 (Brit. Birds 107: 706- 707). This second volume follows the same style as before, with double-page spreads consisting of text facing colour plates in which the most distinctive subspecies are illustrated. In total this book deals with 138 families made up of 6,592 species within 1,358 genera. There are also 57 extinct species included in an appendix. Although it is tempting to think that this is simply a cutdown version of HBW, it is worth noting that of the 12,629 illustrations some 642 are new and a further 1,208 have been improved.

In 2010, a team led by Joseph Tobias from Oxford University published a major paper, entitled 'Quantitative criteria for species delimitation' (Ibis 152: 724-746), in which they proposed a new method for assessing which taxa can be regarded as species. Using their system, numerical scores are allocated to various characters that can be recorded for each taxon, based on appearance and distribution; and if the sum of the scores reaches seven or more, a species is declared. This system has its supporters and detractors, and the purpose of this review is not to take a position on that. However, anyone who is interested in understanding more about the approach taken by BirdLife in making its decisions on species limits will want to read the chapter in Volume 1 of the Checklist (which is reproduced on the Lynx website,

The number of changes in the assessment of passerines between the creation of HBW and this second Checklist is significant. The original volumes of HBW considered 100 bird families for the passerines, but now an additional 38 have been recognised. Mostly these are for small groups of Asian or Australasian species that have been upgraded to reflect current thinking on the relationships with other species. Indeed, some are single species families. One notable change for the Western Palearctic is the treatment of Bearded Reedling (Bearded Tit) Panurus biarmicus as a single-species family in its own right - Panuridae - rather than as part of the parrotbills (formerly Paradoxornithidae). The latter have been moved to join the Old World Warblers in Sylviidae.

For many birders, the biggest interest is in which species the HBW IBirdLife team has decided to split or lump. There are 628 splits in this volume, and just 41 lumps. Families to benefit from extra species include the typical antbirds (Thamnophilidae) (29 ), tyrantflycatchers (Tyrannidae) (42), fantails (Rhipiduridae) (20), crows (Corvidae) (l0), thrushes (Turdidae) (22), Old World flycatchers (Muscicapidae) (39), weavers (Ploceidae) (10) and tanagers (Thraupidae) (23). This means that the HBWIBirdLife taxonomy recognises around 11,000 extant bird species, which is around 330 more than currently listed by IOC and 500 more than the Clements list.

It is also worth explaining that where the authors can see divergence within an existing species they note this using colour coding for each distinctive form. For example, within the 27 races of Eurasian Jay Garrulus glandarius they note six different variations, which are each allocated a name.

The number of interesting splits and lumps is huge, and I will focus simply on a few that affect the Western Palearctic. The authors do not accept Hooded Crow Corvus cornix as a species, lumping it into Carrion Crow C. corone. Similarly, they do not recognise Atlas Pied Flycatcher Ficedula speculigera, leaving it within European Pied Flycatcher Ficedula hypoleuca. On the subject of redpolls, in common with recent thinking they lump 'Lesser' and 'Common' to create a species which they choose to call simply Redpoll Acanthis flammea - rather than Common Redpoll as is the increasing trend. Among the notable splits is Siberian Chiffchaff Phylloscopus tristis, which is separated from Common Chiffchaff P collybita. One species that remains unchanged is the Scottish Crossbill Loxia scotica - which therefore must have scored at least seven points in the 'Tobias test'. So the UK's only endemic bird species remains intact... for now, at least.

There is no doubt that this second part of the Checklist is an outstanding piece of work, and that picking it up for just an hour or so is simply not an option. Once I open it I find myself absorbed in thought for several hours. These days we so often turn to online resources (such as HBW Alive) when we want information, and while these websites provide instant answers to many questions, the ability to look at all of the members of one family together in a book is still a winner for me.

Keith Betton