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1 May 2004 Birds of the Salton Sea: Status, Biogeography, and Ecology
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Birds of the Salton Sea: Status, Biogeography, and Ecology.—Michael A. Patten, Guy McCaskie, and Philip Unitt. 2003. University of California Press, Berkeley, California. xi + 363 pp., 71 text figures. ISBN 0-520-23593-2. $65.00 (cloth).

Located in the baking Colorado Desert just above the Gulf of California, formed by an engineering accident that flooded a basin formerly inundated by periodic wanderings of the untamed Colorado River, maintained by inflows of agricultural and municipal wastewater, and now the center of an environmental controversy emblematic of water shortages throughout the West, the Salton Sea is a singular water body with a rich and abundant avifauna. Birds of the Salton Sea is an important work, as the authors have combined their talents and experience—over 1600 field days since the 1960s—to produce one of few thorough treatments of the birdlife of a major inland lake basin in western North America. The book's strengths are its summaries of each species' patterns of regional occurrence, attempts to place this information in a broader geographic context, and its up-to-date assessments of taxonomy and subspecies status. Its main weakness is in the presentation of quantitative data, particularly of population estimates.

The book is divided into five main sections: “A History of the Salton Sink,” “Conservation and Management Issues,” “Biogeography of the Salton Sea,” “A Checklist of the Birds of the Salton Sea,” and “The Species Accounts.” Despite the different appellations, these all apply to the more inclusive Salton Sink, the larger basin in which the Salton Sea lies. The first two sections, respectively, provide concise descriptions of the history of the region from the Pleistocene to the formation of the present day Salton Sea and of the threats to the ecosystem and possible remedies. The latter section seems to overemphasize the threat of contaminants, as recent studies, despite expectations, found relatively low levels of pesticides in sediments, and there have been no links to substantial reproductive harm to the area's birds. Not discussed is eutrophication from high nutrient loads of agricultural and municipal discharges to the sea, which causes extensive algal blooms, oxygen depletion, and fish die-offs.

The biogeography section describes the prior fish and avifauna, current conditions (climate, inflow to the sea, fish and invertebrates), links to the Gulf of California, vegetation and habitat, and migratory pathways and biogeographic affinities of birds. Treatment of these topics is uneven. Extreme summer temperatures are emphasized but not the mild winters, which in part explain the abundance of birds at that season. Fish species are listed but not the timing of their introductions; the latter is discussed for some invertebrates, but no mention is made here at all of the introduced pile worm (Neanthes succinea), the dietary mainstay of the Eared Grebe (Podiceps nigricollis), the sea's most numerous bird. Discussion of the sea's limnology (seasonal patterns of stratification, oxygen depletion, circulation, and faunal abundance and distribution) would have been a valuable addition.

I found the classification of the region's vegetation more confusing than helpful. The book recognizes eight principal vegetation formations (i.e., communities); the names of the five native ones mainly reflect moisture or soil preferences rather than dominant plant species or growth forms. I was baffled by the word heliophytic, meaning essentially “plants flourishing in sunlight” but here an arcane descriptor for marshes. The prefix would apply equally to all desert plant communities. Also, it was unclear to me why the exotic saltcedar, which most consider primarily a riparian dominant, is described as an important component of three formations. Likewise, I failed to understand why mesquite was included in the xerophytic (drought-tolerant) formation rather than the mesophytic formation, inclusive of riparian, which seems a much better fit given both the authors' assertion that the species was the dominant tree along the New and Alamo Rivers and that other ornithologists consider mesquite a component of desert riparian habitat (e.g., Rosenberg et al. 1991, Birds of the Lower Colorado River Valley, University of Arizona Press, Tucson, Arizona). Perhaps the best gauge of the utility of these formations for describing habitats for birds, though, is their absence from all of the habitat descriptions in the many species accounts I checked.

At times provocative, the discussions of migratory pathways and flyways of waterbirds are occasionally simplistic, poorly documented, and show a northern bias (northern breeding areas emphasized over southern wintering areas). It is claimed as fact (p. 16) that “most” northbound waterbirds in spring are funneled through San Gorgonio Pass, “making it one of the most important migratory corridors in the West,” yet no data or observations are offered in support. The authors argue that shorebirds occurring at the Salton Sink are “largely” from western Canada and Alaska, but there is no discussion in this context of the many species—Mountain Plover (Charadrius montanus), Willet (Catoptrophorus semipalmatus), Long-billed Curlew (Numenius americanus), Marbled Godwit (Limosa fedoa), Wilson's Phalarope (Phalaropus tricolor)—with breeding distributions centered on the Intermountain West or Great Plains. Perhaps the most interesting discussion here is that of the differences in geographic affinities of landbirds: breeding species and subspecies are predominantly associated with the Colorado Desert, whereas migrant and wintering subspecies are mainly from the coastal slope of southern California.

The checklist section provides a handy list of all species and subspecies recorded in the region and includes seasonal status codes and the form of documentation (e.g., specimen, photo) and its depository or reference. This section ends with speculation on the 20 taxa most likely to be recorded next.

The species accounts, comprising the bulk of the book, synthesize a wealth of information to provide excellent summaries of each species' patterns of regional occurrence. Accounts start with a capsule description of seasonal status, followed by details on temporal and spatial occurrence, abundance, and, if known, population trends. Many place the species' status in a broader geographic context using statements of common knowledge. Some specifics about the sea beg for proper citation (e.g., “the most important wintering site for the Snowy Plover in the interior of western North America”; see Western Birds 26:82–98 for such documentation) or for refutation (e.g., the Long- billed Curlew's area of “greater concentration inland”). For most species the ecology section consists of a concise, informative description of habitat use only. Coverage of other relevant topics is uneven, either because knowledge varies widely across species (e.g., diet) or it is treated inconsistently (e.g., nighttime roosts are discussed for the uncommon Sandhill Crane (Grus canadensis) but not for the Cattle Egret (Bubulcus ibis) or White-faced Ibis (Plegadis chihi), thousands of which fly to relatively few roosts in the Imperial Valley).

The rigorous treatment of subspecies taxonomy is the best currently available for any region of California and often will prove useful to those outside the state; many anxiously await such treatments for all of California and North America, both long overdue. The general reader, though, may find some taxonomic discourses tangential at best (e.g., the lone record of California Towhee (Pipilo crissalis) spawning a critique of the validity of all its subspecies north of Mexico).

Although quantitative information can add appreciably to avifaunal works, the documentation of numbers and their style of use in tables and figures often are problematic. The authors did not apply the same scientific rigor to this aspect as to clarifying taxonomic issues or appraising records of rarities. Numbers reported often imply precision that is lacking, and it is impossible to discern what alchemical formulas were used to combine data from different sources to obtain population estimates or to convert anecdotal data to graphs of relative abundance (e.g., Fig. 63) or seasonal occurrence (e.g., Fig. 55). Some numbers in tables or figures conflict with those in the text, are improperly labeled (Table 5; “nesting densities” are actually raw numbers), or lack a proper citation (e.g., bird mortalities, Fig. 7).

Most troubling are the “approximate mean numbers” of waterfowl, shorebirds, and gulls (Tables 7, 9, 11). Waterfowl numbers are from a short period of aerial surveys (when decades of annual surveys are available) modified by Christmas Bird Count and anecdotal data, with source attributions for individual species lacking. Regardless, the sum of the winter “means” for all ducks of about 130 000 (Table 7) conflicts with the text (p. 27) description of wintering numbers being “in the hundreds of thousands, if not millions.” Conversely, Table 7 estimates the approximate mean number of wintering Ruddy Ducks (Oxyura jamaicensis) at 75 000, yet actual mean numbers from the only available long-term censuses (n = 16 years) that include the open water of the sea are double that (R. McKernan in Shuford et al. 2002, Hydrobiologia 473:269). For shorebirds, it is unclear if numbers refer to peak single-day estimates or totals for the entire spring migration. Regardless, many numbers for shorebirds and, particularly, gulls appear to be crude estimates. For example, wintering Ring-billed Gulls (Larus delawarensis) are estimated at 500 000 in Table 11 vs. “hundreds of thousands (perhaps millions)” in the respective species account. Both of these seem at odds with the species' estimated world population of 3–4 million individuals (Ryder 1993, Birds of North America No. 33) and with two winter counts of 23 000– 29 000 Ring-billed Gulls on the entire sea, exclusive of the Imperial Valley (Shuford et al. 2002, Hydrobiologia 473:265). In sum, I urge readers to take most of the book's population estimates with a grain of salt and to look elsewhere for such data.

The captions for the excellent black and white photographs of habitats and birds generally are pithy, though some are incomplete or poorly supported by details in the text. Figure 38's caption incorrectly implies that nesting Snowy Plovers (C. alexandrinus) at the Salton Sea are listed as federally threatened (applies to the coastal population only), and that for Figure 71 indicates that the spread of the Bronzed Cowbird (Molothrus aeneus) into the region has accelerated with the colonization of an additional host, the Brewer's Blackbird (Euphagus cyanocephalus), yet such a relationship is not discussed elsewhere.

Quibbles aside, and population estimates notwithstanding, this book will long remain the standard treatise on the avifauna of the Salton Sea region. It is a must read for anyone seriously interested in the status of birds in western North America and one to return to often. Of greater significance, it will further emphasize the crucial importance of the Salton Sea to birds and draw needed attention to the conservation of this threatened ecosystem.

W. DAVID SHUFORD "Birds of the Salton Sea: Status, Biogeography, and Ecology," The Condor 106(2), 444-445, (1 May 2004).
Published: 1 May 2004

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