Klaus Malling Olsen and Hans Larsson. 2004 (reprinted with corrections). Princeton University Press, Princeton, New Jersey. 608 pp., 83 color plates, 823 color photographs, tables, range maps. ISBN 0-0-691-11997-X. Cloth, $55.00.—Gulls are tough. Geographic variation, a plumage sequence that may span four years or more, closely similar species, hybridiziation, wear, leucism, and more combine to make them among the most challenging birds to identify.

Reading this fine book makes me wonder if young ornithologists know how fortunate they are. In the 1950s, there were few ways to learn gull identification. The best was Dwight's (1925) monumental study of plumages of gulls of the world, which covered all species and was written for curators. The few birders of that era recognized its value, but the book had a limited printing and quickly became a collector's item. Despite its comprehensiveness, its graphics were rudimentary and limited to drawings of patterns of the primaries and rectrices (an important innovation in itself) and a few color plates illustrating head, legs, and soft-part colors of some North American species. To learn about European rarities, we fell back on The Handbook of British Birds (Witherby et al. 1939), which was a great help, but there were still holes. Thayer's Gull (Larus thayeri), for example, had been described as early as 1915. Nevertheless, into the late 1960s, most birders and curators had no clue how to identify it. Since then, there have been other books, of which Grant's (1982) Gulls: A Guide to Identification was a notable advance. It included many black-and-white photos, but its coverage was limited to Europe and eastern North America, and even in the expanded second edition (Grant 1986), Thayer's Gull was essentially ignored.

Now comes Olsen and Larsson's Gulls of North America, Europe, and Asia. This is such an impressive step forward that it is hard to imagine the next steps in the progression of the gull literature, except to expand this book to include the southern hemisphere. Although the emphasis is on identification, the book incorporates many of the recent ideas on species limits in gulls adopted in Europe (some controversial and not yet considered by the AOU). It also treats geographic variation, unfortunately omitting citations of the original descriptions of the various races. Individual species accounts are detailed and include descriptions of plumages, measurements, a range map, estimates of population size, color plates of all plumages, copious color photographs, as well as a quick synopsis of salient points of identification. Some examples of the book's comprehensiveness: the account of American Herring Gull (L. smithsonianus, here considered specifically distinct) spans 14 pages and includes two plates and 20 photos; the Caspian Gull (L. cacchinan and its races or similar species) 31 pages, four plates, and 53 photos; the little-known Relict Gull (L. relictus) 8 pages, one plate, and 11 photos.

The photos are excellent, and whenever possible give the date and location, which is very helpful. The plates of individual species, wonderfully executed by Hans Larsson, continue the high standard for which he is already justly renowned. Comprehensive plates comparing adult plumages of large gulls (four pages) and their typical wing patterns (seven pages) are a fine addition. The latter makes one wish for a companion plate of underwing patterns, at least for those species in which they can be important in field identification (e.g. L. thayeri, L. schistisagus).

Even with all this detail, Rule One still applies: some gulls are unidentifiable, even in the hand. In my years as a taxonomist, I never examined a museum collection without finding at least one misidentified gull. Users of this book may have the same comment. For example, images identified as first-winter glaucescens (fig. 160) and schistisagus (fig. 501), taken in the same place one day apart, are so similar that rather than being of different species they could be of the same individual.

There are occasional confusing statements and errors. The mantle color of Thayer's Gull is darker than that of the Herring Gull, which makes it much (not slightly, as stated) darker than that of the Iceland Gull (L. glaucoides). What does it mean that Bonaparte's Gull (L. philadelphia) “breeds in Canada up to 600 m”? In the California Gull (L. californicus) account, there are several slips. The map given for the breeding range applies only to the inland race (albertaensis); the year-round distribution is actually the breeding range of the nominate race. Given that this species nests almost entirely in the interior of North America, it should be considered entirely (not “partly”) migratory. Juvenal plumage is more variable than shown, and can range from very pale to dark in one colony. It may be that numbers were at one time reduced to 50,000 pairs by egg collecting, as Conover (1983) contended. Even so, citations by others (e.g. del Hoyo et al. 1996) of the same data do not represent confirmation but repetition, and do not give the imprimatur of authenticity.

Two other points regarding California Gulls illustrate a more general problem in the recent and expanding literature. First, Larsson and Olsen report as fact that albertaensis has a leapfrog migration. Others are not as accepting. In Birds of the Salton Sea, Patten et al. (2003) note this as a possibility, but rightly warn against the identification of subspecies without specimen evidence. Second, in commenting on leg color (usually given as greenish-yellow in adults), they speculate that the high proportion of yellow-legged birds in Mexico is attributable to diet. Johnston's (1956) finding that soft-part coloration is hormonally charged, though referenced, is ignored. In the colonies, legs of the earliest breeders are often bright yellow, with those of later breeders being greenish-yellow or duller (J. R. Jehl, Jr. pers. obs). Both these points are based on papers deriving solely from field observations. One cannot fault the compiling authors for citing such papers: completeness is a virtue. But so is skepticism, and the ball falls first in the court of editors (better described as “publishers”) of some popular journals who are unfamiliar with the literature and accept unsupported observational papers without critical examination.

Gulls of North America, Europe, and Asia represents a tough job well done. At a bargain price, it is not only a welcome addition but a near necessity in an ornithological library. As with any controversial group of birds, there will be controversy in some findings. Dwight might not buy the taxonomy, but he would be pleased with the product.