This field guide describes and illustrates geographic variation among bird subspecies in southern Africa, the region that extends from Namibia, Botswana, and the Zambezi River from Zimbabwe and central Mozambique southward through South Africa. Subspecies are characterized as “discrete geographical populations of a species that differ consistently from other populations of that species in one or more morphological aspects, usually in the colour or patterning of plumage…” and as “morphologically and geographically defined populations or ‘races' within a species.” Color plates show 613 of the 870 subspecies in 224 species. Southern Africa is diverse in topography and habitat, and this ecogeographic variation is reflected in its birds.
The text includes common and scientific names (with authorship), seasonal status, a description of key features, and habitat. A glossary explains ornithological terms, and some are labeled in diagrams. Size (total length and body mass) is indicated for the species. The color plates by Ingrid Weiersbye are large and attractive images of adults, males in particular. The geographic variations in nightjars (Caprimulgus spp.), wood-hoopoes (Phoeniculidae), boubous (Laniarius spp.), penduline tits (Anthoscopus spp.), cisticolas and other African warblers (Cisticolidae, Megaluridae, and crombecs Sylvietta in Macrosphenidae), and larks (Alaudidae) are notably well illustrated. Three appendices (18 pages) list the museum specimens used as models for the color plates, the etymology of subspecies names, and 99 additional polytypic species (“having two or more subspecies”) that are not included in the text or color plates. An index lists the genera, species, subspecies, and common names of the birds that are described and figured in the book.
The introduction outlines a history of the study of geographic variation in southern Africa. Maps show political boundaries and towns, regional elevation, rainfall, and regional habitats. Biographic sketches are included for three ornithologists who were based in museums in southern Africa and had a primary interest in geographic variation: Austin Roberts, Peter Clancey, and Michael Irwin. A few birds with geographic variation in plumage and bill color are suggested as candidates for species splits in future taxonomic work. The list of references has 14 items, six being taxonomic works by Clancey; one is the source of his comment, quoted in the first line of the introduction in the book, “Species evolve from races or subspecies.” This comment provides an incentive to consider geographic variation in birds, as is the idea that the birds called subspecies today may be recognized as distinct species tomorrow by systematists, in an ornithological variant of cultural evolution.
As noted by the authors, a popular regional interest in geographic variation in birds had its origin in the field guide of Roberts (1940), which included subspecies and covered the same geographic region. In revised editions of “Roberts” from 1957 onward through the fifth (1984), descriptions of geographic variation and subspecies names were retained and updated to include recently described forms, but these names were deleted in the sixth edition (1993) and then included again in the seventh, no longer a field guide, the comprehensive reference book (Hockey et al. 2005, generally known as “Roberts VII”). In the present book, most common and scientific names are those in Roberts VII, but some differ; and some included subspecies are not in Roberts VII.
Most taxa in the guide are resident breeding birds in southern Africa. The maps show the distribution of breeding and nonbreeding subspecies; the colors show their distribution, not their seasonal status. For example, one subspecies of Little Bittern (Ixobrychus minutas minutas) in the region is a nonbreeding migrant from the Palearctic, and the other, I. m. payesii, is a breeding resident and partial local migrant in southern Africa. In some species, two or more subspecies of nonbreeding Palearctic and other migrants that winter in the region are shown, including petrels, cuckoos, rollers, and warblers. On the other hand, several species with conspicuous geographic variation in plumage and recognized as subspecies in Roberts VII are not included; for example, the African Quailfinch (Ortygospiza atricollis), Blue Waxbill (Uraeginthis angolensis), and Melba Finch (Pytilia melba). Also, variation in plumage is not always best described simply in terms of subspecies. In one such case, three geographic variations of Jacobin Cuckoos (Clamator jacobinus) occur in southern Africa, but only white-bellied birds are illustrated. These birds are distinguished more in size than in plumage; size differences are not mentioned. The black plumage morph of C. j. serratus (originally described as a distinct species) is the one seen most often in southern KwaZulu Natal and the coastal Eastern Cape in South Africa. Contrary to the text, C. j. serratus is the only subspecies of Jacobin Cuckoo with a black morph; these black birds are occasionally seen in their nonbreeding season as far north as west-central and east Africa, but do not breed there and are intra-African migrants. Both the buff morph and the olive morph of the Olive Bushshrike (Chlorophoneus olivaceus) are described, but only the buff morph is illustrated; the olive morph is the common one in the Western and Eastern Cape. For both these species, the two plumage morphs are illustrated in standard field guides of southern African birds. The book is generally accurate, and I noted few errors—on page 50, in the map for the African Goshawk (Accipiter tachiro), the blue and green areas should be transposed; and in the color plate on page 185, the subspecies names of the Garden Warbler (Sylvia borin) should be transposed.
The book is useful in its depiction of geographic variation in plumage in southern African birds. It does not allow the identification and separation of all similar species in the region; for that purpose a standard field guide is needed. It does not include size differences among subspecies, perhaps because size is not useful in field identification. The book does not mention behavior and song of birds; nevertheless, these behaviors may differ between geographic populations. Most color figures were based on specimens identified and curated in the Durban Museum, and this may account for the emphasis on subspecies, some of them described by Clancey, for many years that museum's systematic ornithologist, who made fine distinctions in color variation in plumage. Although the book's title includes geographic variation, the variation is treated within the context of subspecies, a word perhaps less appealing in the title of a field guide. The book is a useful and well-illustrated supplement to the regional reference (Roberts VII) and standard field guides for the region.