Birds of the Seychelles

Birds of the Seychelles.--Adrian Skerrett and Ian Bullock. Illustrated by Tony Disley. Princeton University Press. Princeton, New Jersey. 320 pp., 53 color plates, 18 line drawings, 5 maps. ISBN 0-691-088632. Paper, $39.50.--The unique avifauna of the Seychelles has long deserved a field guide of this quality. Its sole predecessor (Penny 1974) did not do justice to the islands or their birds, in particular by omitting common migrants that were described in other field guides (Diamond 1975). Skerrett and Bullock's book goes to the other extreme, including figures and full descriptions of all species recorded in the archipelago and several of uncertain status.

Nearly twice as many species (250) have now been recorded in the Seychelles as in 1974. The unique biogeographic situation of the Seychelles-a tiny but ancient archipelago set on a migration route linking two continents and an island of continental dimensions (Madagascar)-has shaped its extraordinary avifauna in ways that the authors describe clearly, succinctly, and accurately. The book begins by describing the origin and location of the islands, with five clear and accurate maps at varying scales from the whole Indian Ocean west of Christmas Island, to individual islands (the largest, Aldabra Atoll). The authors distinguish between the granitic islands at the northeast end of the archipelago, and the much more numerous "outer" islands (atolls and sandcays). They draw attention to the geological uniqueness of the granite islands, which, apart from St. Paul's Rocks in the South Atlantic, are the only oceanic islands composed of continental rather than oceanic rocks, a relic of the break-up of Gondwanaland into Africa, India, and Madagascar. Because of this origin, some of the biota (notably amphibians and some palms) are descendants of indigenous survivors rather than waifs arriving by transoceanic dispersal; although that gives the islands' biota high rates of endemism in some groups, it is not clear that any bird species can be considered relics. The relevant features of the islands' geological history are briefly sketched, highlighting the reduction in land area (from 300,000 km^sup 2^ to

The major groups of islands, and the larger individual islands, are described briefly, followed by a note on the climate (tropical oceanic, as would be expected at 4-10 deg S), a list of plants mentioned in the text, information about the Seychelles Bird Record Committee (on which both authors are active), a glossary of (ornithological) terms used, and two fascinating pages on the origins of the bird fauna of the Seychelles. This will interest and excite any birder or ornithologist interested not only in "what is that bird," but "where is it from, and how did it get here"--the extra questions that give a special dimension to island ornithology.

The authors paint a vivid picture of "tiny specks of rock" separated from other landmasses 65 Mya and colonized over the millennia by exhausted windborne vagrants. They give examples of species that have evidently colonized twice, from different directions, because different races now coexist there, for example the Green Heron [Butorides striatus] with a race of African origin (degens) in the granitic islands and one of Asian origin (crawfordi) in the outer isles. By detailing the varied origin of endemic and other native birds-from Madagascar, India, Africa, and Malaysia-they illustrate vividly the chaotic colonisation of those islands at a crossroads of the western Indian Ocean. The processes of immigration and colonization of course continue, with a Black-crowned Night Heron [Nycticorax nycticorax] arriving as a vagrant in 1992 and breeding by 1996; and a Longtailed Cormorant [Phalacrocorax africanus] is described here as reaching Aldabra in 1999, though in the main text (p. 159) it is described as "vagrant to Aldabra and the granitics recorded in most months."

This excellent essay is followed by a checklist before launching into the colored plates. Each plate illustrates all the plumages likely to be seen in Seychelles of three to nine species (usually four or five); the authors say all those in the same pose are to scale but we might disagree on how similar poses have to be to be the same. The first plate is of species now extinct on Seychelles, of which three are globally extinct. Many publishers of field guides would not pay for a plate of birds that would not be seen (thank you, Princeton University Press!). The practice of showing all similar or related species recorded in the Seychelles might lead to confusion and misidentification among visiting birders, were it not for the very useful introductory note to the explanatory text opposite each plate that summarizes the status of the species illustrated, Thus, if I look only at the plate showing five species of storm-petrel I might think I could expect to see any of them, but the text opposite warns me that two are vagrants between October and November, one is a vagrant in May, and the other two are of "uncertain status," that is, I am most unlikely to see any of them! I am not sure what arguments the authors used to persuade the publisher to pursue such pictorial profligacy, which is sadly rare in field guides, but both parties are to be congratulated because this is likely to facilitate early confirmation of several species of uncertain status. The text opposite the plates gives common (English) name, scientific name, size (length for most species, wingspan for long-winged species), page of species account, and succinct distinguishing features of each plumage illustrated.