Birds of the Salton Sea: Status, Biogeography, and Ecology 9780520929449

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BIRDS ofthe SALTON SEA

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BIRDS ofthe SALTON SEA

Michael A. Patten, Guy McCaskie, and Philip Unitt

U N I V E R S I T Y O F C A L I F O R N I A PRESS Berkeley Los Angeles London

University of California Press Berkeley and Los Angeles, California University of Cahfornia Press, Ltd London. England All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transm~tted,in any form or by any means, w~thout the prior permission In writlng of the University of California Press, or as expressly permitted by law, or under terms agreed with the appropriate reprographics rights organization. Library of Congress Cataloging-in-Publication Data Patten. Michael A. Birds of the Salton Sea : status, biogeography, and ecology / M~chaelA. Patten, Guy McCaskie, and Philip Unitt. cm. p. Includes bibliographical references (p. ). ISBN 0-520-23593-2 (cloth : alk. paper) I. Birds-California-Salton Sea. I. McCaskie, Guy 11. Unitt, Philip. 111. Title. Q L 6 8 4 . c ~P38 2003 598'.09794'99-dcz1 zoozo1~31z Manufactured in the United States of America 13 12 11 10 0 9 0 8 07 oG 05 04 1 0 9 8 7 6 5 4

3 2 1

The paper used in this publication meets the rniniml~nirequirements of ANSI/NISO 239.48-1992 (R 1997) @

CONTENTS

Foreword

/ vii

A CHECKLIST O F T H E BIRDS O F T H E SALTON SEA

Preface and Acknowledgments / ix

The Primary Checklist The Next Twenty

A HISTORY O F T H E SALTON SINK

Lake Cahuilla

/

/

/ 33

1

T H E SPECIES ACCOUNTS

2

Formation of the Salton Sea

/

68

The Geographic Region

/ 4

Data Collection CONSERVATION A N D M A N A G E M E N T ISSUES

/ 7

Taxonomy and Nomenclature Subspecies / 7s

Proposed Solutions / 9

The Main List / 72

BIOGEOGRAPHY O F T H E SALTON SEA

/

The Fauna of Lake Cahuilla / Current Conditions / 13 The Salton Sea and the Gulf of California / 15 The Avifauna / 26

Nonnative Species

12

/ 18

12

/ 68

/ 69

Current Threats / 8

Vegetation and Habitat

/ 33

/ 70

/ 316

Hypothetical List / 317 Appendix: Common and Scientific Names of Plant Species Mentioned in the Text / 323 Literature Cited / 325 Index / 349

/ 33

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FOREWORD

Anybody who has been to California's Salton Sea will have lasting memories, and perhaps a recurring nightmare or two. The sea assaults one's senses with a potpourri of richly organic odors, eye-popping sunsets, the biting cold of a winter morning, or the sauna ambience of a summer afternoon. And there are the birds-the spectacular flocks in the air or rafting on the sea, the yap-yapping of Black-necked Stilts punctuating the summer heat, the whistling of the wings of winter waterfowl. Birders, hunters, and tourists from far and wide have visited the Salton Sea to enjoy the spectacle of thousands of geese in the agricultural fields and wildlife refuges at the south end, along with winter flocks of ducks, egrets, ibises, gulls, and curlews. But many birders, and most notably this book's three authors, have learned that the Salton Sea's steamier, seedier "other siden-the sweltering heat and stifling humidity that grip the region from May through September-offers even greater rewards: significant yet fragile breeding colonies of terns, skimmers, herons, ibises, and cormorants; northward-wandering subtropical waterbirds; mudflats teeming with southbound shorebirds; even surprise visits by seafaring birds such as petrels and albatrosses. I first birded the Salton Sea in January 1968. By this time Guy McCaskie was already well

known for the wizardry ofhis precise and systematic approach to finding new and unusual birds and birding places. Phil Unitt was just developing an interest in ornithology that would lead to a career and to the authorship of numerous important works, including the monumental Birds of San Diego County. And the primary author, Michael Patten, had yet to start lundergarten. All trained in different decades, each of these coauthors approaches field ornithology with a different perspective. They have collaborated to produce a timely and masterful analysis of the birdlife of one of the most important bird areas in the Western Hemisphere. Some ornithological exploration of the Salton Trough predates the formation of the presentday sea, and in many ways true study of the sea's avifauna began with Joseph Grinnell's voyage on the Vinegaroon in April 1908.But not until now has there been a complete analysis of the odd biogeographic juxtapositions that constitute the area's avifauna. The inclusion of subspecies treatments continues an important tradition that unfortunately has been lost from much of the recent literature. This book documents the past and present avifauna of the Salton Sea at a crossroads in its history. Threats to the sea are ultimately derived from the decisions by governments, corporations,

and special interests to accommodate a rapidly expanding human population in the water-starved southwestern United States at the expense ofthe natural integrity and unique and diverse wildlife of the region. The theft of this water-whether to lavish it upon the lawns of San Diego, to wash the cars of Los Angeles, or to spout it obscenely from the garish fountains of Las Vegas-has robbed the Colorado River delta of its lifeblood and now threatens the delta's de facto replacement, the Salton Sea. The future of the Salton Sea is uncertain. We do not know if this schol-

arly and thorough effort by Michael Patten, Guy McCaskie, and Phil Unitt will serve as documentation of what is lost or a catalyst for ongoing research in a region of great diversity. In either or both of these roles, however, Birds of the Salton Sea will quickly become and long remain a classic. K I M B A L L L. G A R R E T T

Natural History Museum of Los Angeles County

PREFACE A N D ACKNOWLEDGMENTS

It is at best a rather cheerless object, beautiful in a pale, placid way, but the beauty is like that of a mirage, the placidity that of stagnation and death. Charm of color it has, but none of sentiment; mystery, but not romance. Loneliness has its own attraction, and it is a deep one; but this is not so much loneliness as abandonment, not a solitude sacred but a solitude shunned. Even the gulls that drift and flicker over it seem to have a spectral air, like bird-ghosts banished from the wholesome ocean. "E'en the weariest river Winds somewhere safe to sea";

but for the Salton the appointed end is but a slow sinking of its bitter, useless waters, a gradual baring of slimy shores, until it comes once more, and probably for the last time, to extinction in dead, hopeless desert. (1919), 3 0 ~ U L Y1911

J. SMEATON CHASE D E S C R I B I N G THE SALTON S E A ON

The Salton Sea evokes myriad images, many in stark contradiction. It is at once unbearably hot, foul of odor, and seemingly uninhabitable, yet it is a haven to one of the largest populations of waterbirds in western North America. Indeed, its unique biogeographic setting supports more than four hundred native species, exceeding the total for many states. Some one hundred species, including the Brown Pelican, the Gull-billed Tern, and the Black Skimmer, oddities in the landlocked Southwest, see fit to breed in the region. Yet all is not well in the Salton Sea. The water quality has deteriorated, and much native habitat has been lost, particularly thickets of mesquite and riparian woodland of cottonwood and willow. More alarming, massive die-offs of fish and birds have been commonplace, initially

sparking concern, later yielding a fervent push to preserve this important ecosystem before it is lost. But basic conservation efforts require basic data. Before we can hope to preserve the ecosystem, we need to know more about the species that constitute it-their relative abundances, their habitats, their places of origin, the last being especially important for migratory taxa. Birds are the most conspicuous animals in the ecosystem, and we have been studying them for many years. We pooled our expertise in an attempt to produce a treatise that would both form the foundation for informed conservation decisions and introduce scientists and laypersons to the birdlife of this fascinating region. This book was inspired by many others, but it differs from them all. Particularly notable

influences were The Distribution of the Birds of California, by Joseph Grinnell and Alden H. Miller (1944),The Birds of Arizona, by Allan R. Phillips, Joseph T. Marshall, and Gale Monson

(1964)~The Birds of Southern California: Status and Distribution by Kimball L. Garrett and Jon L. Dunn (1981),Once a River, by Amadeo M. Rea (1983)~The Birds of San Diego County, by Philip Unitt (1984),and Birds of the Lower Colorado River Valley,by Kenneth V. Rosenberg, Robert D. Ohmart, William C. Hunter, and Bertin W. Anderson (1991).To varying degrees these works included detailed information on status, distribution, habitat, and subspecies. In the present volume, we have strived to incorporate the best elements of each of these books to construct exhaustive accounts of each species' current and historical status. We have included information on ecology in the Salton Sink, the biogeography of the sink and neighboring regions and its effect on distribution and occurrence, and taxonomy at the species and subspecies levels. Together these aspects paint a detailed portrait of the avifauna of the Salton Sea.

This project could not have been accomplished without the assistance of many field ornithologists. Several individuals deserve special recognition for their input and their willingness to share their expertise. To that end, we express our deepest gratitude to Brian E. Daniels, Kimball L. Garrett, Roger Higson, Kenneth Z. Kurland, Robert L. McKernan, Kathy C. Molina, Amadeo M. Rea, W. David Shuford, and Sherilee von Werlhof. We thank the following individuals for supplying information on specimens in their care and other museum-related information, allowing access to their collections, or lending specimens: William G. Alther ofthe Denver Museum of Natural History, George F. Barrowclough, Christine Blake, Emanuel Levine, and Paul Sweet of the American Museum of Natural History in New York, Louis R. Bevier and Nate Rice of the Academy of Natural Sciences, Philadelphia, Kevin J. Burns of San Diego State University, Steven W.

X

PREFACE A N D ACKNOWLEDGMENTS

Cardiff and J. V. Remsen Jr. of the Louisiana State University Museum of Natural Science in Baton Rouge, Carla Cicero and Ned K. Johnson of the Museum of Vertebrate Zoology in Berkeley, Charles T. Collins of California State University, Long Beach, Paul W. Collins and Krista Fahy of the Santa Barbara Museum of Natural History, Ren6 Corado of the Western Foundation of Vertebrate Zoology in Camarillo, California, Tamar Danufsky of Humboldt State University in Arcata, California, Charles M. Dardia of Cornell University, James P. Dean and Craig Ludwig of the National Museum of Natural History in Washington, D.C., Kimball L. Garrett of the Natural History Museum of Los Angeles County, John C. Hafner and James R. Northern of the Moore Laboratory of Zoology at Occidental College, Mary Hennen of the Chicago Academy of Sciences, Fritz Hertel of the Dickey Collection at the University of California, Los Angeles, Gene K. Hess of the Delaware Museum of Natural History, Janet Hinshaw of the University of Michigan Museum of Zoology, Mark A. Holmgren of the University of California, Santa Barbara, Thomas R. Huels of the University of Arizona, Robert L. McKernan ofthe San Bernardin0 County Museum, Alison Pirie and Douglas Siegel-Causey of the Museum of Comparative Zoology at Harvard, Mark B. Robbins of the University of Kansas, Gary W. Shugart of the Slater Museum at the University of Puget Sound, Paul F. Whitehead of the Peabody Museum at Yale, David Willard of the Field Museum in Chicago, Chris Wood of the Burke Museum at the University of Washington, and Robert M. Zink of the Bell Museum at the University of Minnesota. Many other individuals supplied unpublished field notes or other important information without which this project could not have been completed: Daniel W. Anderson, James C. Bednarz, Louis R. Bevier, Jean Brandt, Aaron Brees, M. Ralph Browning, P. A. Buckley, Jutta C. Burger, Eldon R. Caldwell, Eugene A. Cardiff, Steven W. Cardiff, Carla Cicero, Luke W. Cole, Daniel S. Cooper, Ren6 Corado, James P. Dean, Jon L. Dunn, Richard A. Erickson, Shawneen E.

Finnegan, Daniel D. Gibson, John Green, Sue Guers, Robert A. Hamilton, Loren R. Hays, Gjon Hazard, Matthew T. Heindel, Tom and Jo Heindel, Steve N. G. Howell, Stuart H. Hulbert, Joseph R. Jehl Jr., Ned K. Johnson, Paul D. Jorgensen, Lloyd F. Kiff, Howard King, John R. King, Sandy Koonce, Jim Kuhn, Paul E. Lehman, Tony Leukering, Linette Lina, Margaret McIntosh, Curtis A. Marantz, Chet McGaugh, Douglas B. McNair, Eric Mellink, Bob Miller, Jason A. Mobley, William J. Moramarco, Brennan Mulrooney, Richard J. Norton, Kenneth C. Parkes, Bruce G. Peterjohn, Stacy J. Peterson, the late Allan R. Phillips, Molly Pollock, Peter Pyle, Kurt A. Radamaker, Carol A. Roberts, Michael M. Rogers, Gary H. Rosenberg, Paul Saraceni, Jack W. Schlotte, N. John Schmitt, Jay M. Sheppard, Brenda D. Smith-Patten, Mary Beth Stowe, Emily Strauss, Brett Walker, Richard E. Webster, Walter Wehtje, the late Claudia P. Wilds, Douglas R. Willick, and Thomas E. Wurster. We thank Karen Klitz and the Archives at the University of California, Berkeley, for supplying historical photographs of the Salton Sea. Kenneth Z. Kurland graciously provided many photographs of recent birds, as did Jack W.

Schlotte of recent habitat. Additional photographs of birds and habitats were supplied by Barbara A. Carlson, Deborah L. Davidson, Greg W. Lasley, Brennan Mulrooney, Brian G. Prescott, Lawrence Sansone, Brenda D. Smith, and Richard E. Webster. Part of Michael Patten's specimen research was funded by a collection study grant from the American Museum of Natural History. Financial support for the completion of this book was generously provided by the Western Ecological Research Center of the United States Geological Survey in San Diego, through a contract administered by Douglas A. Barnum and William I. Boarman. We thank Daniel W. Anderson, Jeff N. Davis, Joseph R. Jehl Jr., Paul F. Springer, Rich Stallcup, and Nils Warnock for reading all or portions of the text. Finally, we thank Doris Kretschmer and Nicole Stephenson of the University of California Press for their invaluable guidance and advice. M I C H A E L A. P A T T E N G U Y MCCASKIE

PHILIP UNITT

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A History o f the Salton Sink

B EC I N TH E S T 0 RY of the Salton Sea with the Salton Trough, the rift extending from the Coachella Valley to the central Gulf of California. The Salton Sink, which lies between the southern Coachella Valley and the northern Mexicali Valley, occupies but a small portion of the trough, but the histories of the two are intertwined. From a geological standpoint, the long history of the Salton Trough ranges from its connection with the Gulf of California during the Tertiary Period (Blake 1914; Durham and Allison 19Go) to the maximum spread of Lake Cahuilla beginning some 40,000 years ago, during the pluvial times of the Pleistocene (Setmire et al. 1990). During the Pliocene, a few million years ago, the entire Salton Trough was, by most accounts, merely the head of the Gulf of California (Fig. I; Durham and Allison 19Go).Massive deposits of silt from the Colorado River eventually accumulated along the southern edge of Gravel Mesa to form a barrier between the former head of the gulf and the current one (Fig. 2; Blake 1914; Kennan 1917; Loeltz et al. 1975; cf. Free 1914). The enclosed sea subsequently dried up, but reminders of the saline environment in the form of "oyster-shells and

other forms of marine life" are strewn across the base ofthe Santa Rosa and San Jacinto Mountains at an elevation of about IOO m (Blake 1914). The depression resulting from the desiccation of this "trapped sea was further honed by the uplifting of the surrounding mountains (Blake 1914)and became a deep basin generally called the Salton Trough (Sykes 1914).In rough terms, this trough includes the Coachella Valley, the Salton Sink (the geographical region covered in this book), the Imperial Valley, the Mexicali Valley, and the southern portion ofthe Rio Colorado delta. (We refer to the U.S. portion of the river as the Colorado River and to the Mexican portion as the Rio Colorado.) The Peninsular Ranges, the Anza-Borrego Desert, the Sierra Jugrez, and various other ranges in northeastern Baja California border it to the west. The Orocopia and Chocolate Mountains, the Algodones Dunes, and Gravel Mesa form the eastern boundary. The northern terminus lies at the base of the great rift known as the San Gorgonio Pass. Much of this trough lies well below sea level, an area known as the Salton Sink or, sometimes, the Cahuilla Basin (Setmire et al. 1991).The sink lies in an actively spreading rift valley (Setmire

FIGURE 2. Formation of a sandy bench dividing the Salton Sink from the present Colorado River floodplain and the Gulf of California. Adapted from Kennan 1917%.

Sea. The moniker Lake Le Conte, after Joseph Le Conte, a well-known professor of California when geography, was also widely used until 1907, Blake himself insisted on his own priority (Gunet al. 1993).Low-lying alkaline flats typify this ther 1984).The name Lake Cahuilla, after the region, although there are a few rocky outcrops local Native Americans, has been used for the and hills, mostly volcanic in origin, such as Tra- prehistoric lake ever since. The shoreline can vertine Rock, Mullet Island, Red Hill, Obsidian still be seen along the eastern flank of the Santa Butte, Mount Signal, and Cerro Prieto (Loeltz et Rosa Mountains (see, e.g., Schoenherr 1992: al. 1975).Tremendous geothermic activity not 421),especially around Travertine Rock, and far below the earth's surface sprouts mud pots there is evidence of the "heavy assaults of surf and "mud volcanoes" (Blake 1914; Nelson 1922) for some considerable period" along the norththat further shape the terrain near the south- eastern shoreline, south of Mecca (Sykes 1914). eastern shoreline of the Salton Sea and the for- Furthermore, the Algodones Dunes and premer Volcano Lake (now dry and occupied by sumably dunes around the Superstition MounCampo Geotermico Cerro Prieto). Even so, the tains are the remnants of beaches from this sink is practically featureless in comparison with forerunner of the Salton Sea (Norris and Norris 1961), and it is clear that the central Coachella most of the Sonoran Desert. Valley was once an area of playas and shallow lakes similar to but commonly larger than the LAKE CAHUILLA Salton Sea (California Department of Water ReThe existence of Lake CahuiUa was first recorded sources 1964). Early incarnations of Lake Cahuilla had a for posterity by William Phipps Blake during surveys for potential rail routes through the South- shoreline peaking at 50 m above sea level (Setwest (Blake 1858).For this reason early literature mire et al. 1990).More recent versions had a often referred to the ancient lake as the Blake lower surface elevation, reaching a mere 12 m FlGURE 1. Northern extent of the Gulf of California during the Pliocene (dotted line), showing area now silted and the Salton Sea. Adapted from Durham and Allison 19Go.

2

A HISTORY OF T H E SALTON SINK

Saltan Sea

Xahuilla

1000

1200

1400

1600

1800

2000

Year (A.D.)

R ,'O {

Hardy

FIGURE 4. Approximate timing of high water at Lake Cahuilla. A.D.800 to A.D.2000. Adapted from Laylander 1997and Smith 1999.

earliest floodwas between 6,670 and 1,000years ago (Waters 1983;Gurrola and Rockwell 1996). The other three were much more recent: the Gulf of '1 California II second flood was between 720 and 1,180years ago, the third about 650 years ago (Wilke 1978; Waters 1983;Gurrola and Rockwell 1996),and FIGURE 3. Typical extent of Lake Cahuilla at high water, Lake Cahuilla was last filled to capacity only with the present Salton Sea superimposed for comparison. about 400 years ago, meaning that it was present during the late 1500s and early 1600s (Norabove sea level. In either form this mighty ris and Norris 1961;Gurrola and Rockwell 1996; lake-160 km long and 56 km wide, covering an Laylander 1997).The appearance and evaporaarea of about 5,400 km2 and reaching a maxi- tion of this lake little by little was well known to further evimum depth of nearly IOO m-dwarfed the the Cahuilla Indians (Blake 1914)~ present Salton Sea, which measures only 72 km dence of its recency in the Salton Trough. long by 27 km wide, covers an area of about Since Lake Cahuilla was last filled, periodic 1,150 km2,and reaches 25 m at its deepest point small floods have inundated the Salton Sink, (Fig. 3; Blake 1914;Woemer 1989).Indeed, the creating smaller lakes or seas in 1840,1842,1852, entire Salton Trough is scarcely larger than 1859,1862,and 1867 (Sykes 1914).Most floodwas Lake Cahuilla, which measured 208 km by ing has been through the New River, "so named for its unexpected appearance flowing into the 112 km (Loeltz et al. 1975). After it dried up, Lake Cahuilla was periodi- desert in the year 1849" (Blake 1915, contra cally filled by floodwaters from the Colorado Schoenherr 1992).The last major flood occurred River; it was thus a largely freshwater lake in 1891(Sykes 1914,1937).when a lake with a (Walker 1961),although it may have been some- surface area roughly half that of the current what brackish at times, especially during early Salton Sea was formed (Chase 1919).Sykes (1914) inundations (Blake 1914).The river deposited noted that some water had "found its ways down copious sediments and left the rich soil that sup- the channel of the New River toward the Salton ports flourishing agriculture in the Coachella, every year since the inundation of 1891,"demonImperial, and Mexicali Valleys today (Blake 1914; strating the capacity of natural Colorado River Cory 1915;Setmire et d. 1990). At least four floods to fill the Salton Sink, a seemingly esoteric major floods occurred during the past four mil- point that should be remembered when pundits lennia, each reforming this vast lake (Fig. 4).The decry the Salton Sea as nonnatural. While the

/

A H I S T O R Y O F T H E SALTON S I N K

3

sink may not have flooded again after the turn of the twentieth century, this result would have been achieved only through the continuous damming and dilung of the great river, not because its capacity to flood was lost. But for human domination of the Colorado, who knows how full the sink would have become when tropical storm Kathleen hit in 1976 or when the river flooded during El Nifio in 1983?People's taking from and giving to this ecosystem were punctuated by a fortuitous engineering blunder that brought back a vestige of the former Lake Cahuilla.

FORMATION OF THE SALTON SEA

The story of the Salton Sea begins with William Phipps Blake. Blake (1858) observed that routine flooding by the Colorado River accumulated extremely rich fluvial and silty clay soils in the Salton Sink that would produce bountiful crops if sufficiently irrigated. This seemingly wild notion was ignored for decades. Quite independently of Blake, and a half-decade earlier, another visionary, Oliver Wozencraft, saw that the rich soils in the Imperial Valley might be irrigated by diverting water from the Colorado River through the Alamo River. Blake warned that irrigation attempts might flood the Salton Sink since it was some I O O m lower in elevation than the Colorado River at Yuma. Wozencraft was less concerned about such potential problems and was undeterred by skeptics who noted that the sand dunes between the Colorado and the Salton Sink, rising a few hundred meters, would impede construction of canals. Instead, he pursued his vision with vigor for several decades, though ultimately he failed to gain the needed support. The dream might have died had it not been for Charles Rockwood and George Chaffey,whom Woerner (1989) calls the "main players . . . in 'The Great Imperial Valley-Colorado River' play." Rockwood and Chaffey resurrected Wozencraft's dream, designing an elaborate scheme to bring irrigation water to the Imperial Valley (a name coined by Chaffey). They too chose the Alamo River as the most reasonable channel by which to convey water. A short canal and an inflow site

4

4 IilSTOKY

OF THL SALTON S I N K

with a headgate were needed to convey water from the Colorado to the Alamo. The headgate was placed near Yuma, and construction began on it and the canal in August 1900 (Cory 1915; Kennan 1917; Woerner 1989). By June 1901 water was being diverted into the Alamo, allowing irrigation and agriculture to begin. The canal worked smoothly for several years, until it was clogged by a deposit of heavy silt, which disrupted inflow. (The Colorado River, which had carved the Grand Canyon and other glorious rock formations in the Southwest, was known for carrying a massive load of silt.) Thus, dredging to unclog the canal was a ceaseless task. In spite of this problem, about 150,000 acres (ca. 620 krn2)ofthe Imperial Valley had been brought under cultivation by 1904. The rapid establishment of an important agricultural economy increased pressure for adequate water delivery. In September 1904 the fateful decision was made to dig a temporary intake in hopes of improving water delivery to the Alamo River (Kennan 1917;Woerner 1989).Finished quickly, it amounted to little more than a ditch 15 m wide and 2 m deep dug at river level, without a headgate, some 6 km south of the main headgate. The ditch soon silted, requiring constant dredging, but the water level could not be controlled because there was no headgate. Floods on the Colorado River in the winter of 1904-5 rushed down the ditch, bringing to the Imperial Valley far more water than was needed for irrigating crops. The excess water was carried by the Alamo and New Rivers to the Salton Sink, which slowly began to fill, just as Blake had warned decades before. Water in the sink was rising at a rate of about I cm per day by October 1905 as water gushed through the ditch, widened by floods to a gaping zoo m and deepened to 8 m! Almost all the river water was now flowing to the Salton Sink, with little to none continuing on to the Gulf of California (Cory 1915; Kennan 1917).Panic set in as rising waters claimed not only farms and ranches but also the saltworks and the Southern Pacific Railroad tracks. Nearly every solution imaginable, from pilings to sandbags to dyna-

mite, was thrown at the problem, but each failed as the raging torrent continued to widen the channel. By 1906 hope was nearly lost, spawning sarcastic news features and editorials publicizing Indio as a new seaport for the gulf (Woerner 1989).In Aupst of that year the flow was nearly halted when zoo railcar loads of rock, gravel, and clay were dumped into the channel, plugging the break by November. But the solution was short lived. By December floodwaters again rose, destroying the newly constructed dam and carving a channel nearly a kilometer wide that dumped ever more water into the Salton Sea, now a vast lake. A successful dam was completed by February 1907. The level of the Colorado River rose some 4 m, and water levels in the Alamo and New Rivers decreased drastically. Once the 1907dam blocked inflow, the Salton Sea had a surface elevation of Go m below sea level and was thus larger than it is today. Sur-

Year FIGURE 5. Surface level ofthe Salton Sea, 1905-1995. Data

from the Imperial Irrigation District, 1996.

face elevations fluctuated dramatically during the first two decades after the sea's rebirth (Fig. 5), reaching a low of 75 m below sea level in 1925 (Holbrook 1928).Irrigation-effluentditches constructed in 1922 and after restored the level of the sea to about 68 m below sea level (Holbrook

FIGURE 6. The Salton Sea on 9 April 1908,shortly after its birth, looking south from the shoreline near Mecca. Protruding from the surface are a multitude of dead shrubs killed by flooding of the sink. Photograph by JosephGrinnell, courtesy of the Archives of the Museum of Vertebrate Zoology, University of California, Berkeley.

A H I S T O R Y O F T H E SALTON S I N K

5

1928);indeed, had it not been for the vast repository that is the Salton Sea, the rich agriculture of the Imperial, Coachella, and Mexicali Valleys would not be possible. The water level is now much more stable, although it is slightly higher in spring and lower in fall (Setniire et al. 1990). And thus the Salton Sea was born (Fig. 6). For the reason why the current lake is called the Salton Sea rather than Lake Cahuilla we once again turn to Blalte (1914). Blalte noted that because the Salton Sea was but a vestige of the much vaster ancient body-much as the Great Salt Lake is a vestige of Lake Bonneville (Blake 1914; Jehl1994)-each deserved its own name. Because the engineering accident that led to the inundation of the Salton Sink and thus formed the Salton Sea has been chronicled in detail by others, we present only a general summary. Readers interested in greater detail should refer to the lively account by IZennan (1917)~ which set the standard for subsequent efforts, and that ofwoodbury (1941)~ who took a broader geographic view. The more technically inclined are referred to Cory's (1915) account, which discusses every engineering aspect of the initial irrigation project and the various efforts to stop the flooding of the Salton Sink.

Most accounts fail to mention that 1905 was a major flood year and that had it not been for the extensive channelization and draining of the Colorado River, the Salton Sink likely would have been inundated anyway. Copious inflow of irrigation water has kept the Salton Sea alive, sparing it the desiccation of Lake Cahuilla. As a result ofvery high evaporation rates, from 1.8 m (Tetra Tech z o o o ) to 2.4 m (Blake 1914) per annum, Blake (1914)asserted that the 25 m "ofwater now covering the Desert, and known as the Salton Sea, will require ten and a half years for its coniplete evaporation." Thus, aqua-engineering of the region has been a decidedly mixed blessing. Because of the engineering debacle that formed it and the agricultural runoff that maintains it, the largest inland body of water in California has been dubbed "in essence manmade [with] a manmade ecosystem" (Setmire et al. 1993). Yet given the long history of flooding in the Salton Sink and its long history ofwaterbird use, it may be more proper to view the Salton Sea as the latest in a long series of laltes that have occupied the basin. With this view, at the least the sea is partly manmade and partly a natural phenomenon, not wholly one or the other.

Conservation and Management Issues

N T H E 1940s A N D 1950s the Salton Sea attracted tourists and fun-seekers from nearby metropolitan areas. The sea became so popular that the Salton Sea State Recreation Area was developed along the northeastern shoreline. After the introduction of marine fishes the sea also became a major sport fishery. The robust economy of the 1950s brought real estate speculators, who marketed the area as a thriving resort. As the Salton Sea aged, however, its appeal waned. The water became brown and turbid, fish carcasses littered the shore, and distasteful odors emanated from mud and backwaters. In the 1980s high water levels encroached on prime shoreline, and much of the shoreline now is dotted with dilapidated buildings and abandoned marinas, built only a half-century ago. Negative publicity about the New River, the most polluted waterway in the United States, contributed to the economic decline of the area. Pollution in this river poses a serious threat to the Salton Sea. At the international boundary, water in the New River carries raw sewage, agricultural drainage water, and power plant effluent, with the attendant detergents, pesticides, and other industrial and agricultural chemicals. Despite natural

cleansing during the river's 80-lun journey, many of these harmful elements reach the Salton Sea. The Alamo and Whitewater Rivers fare better: they carry mainly agricultural runoff, but not raw sewage or industrial effluent. The Salton Sea has thus become a cause celebre for conservation biology. Its plight features commonly in newspapers, popular magazines, and journals (e.g., Boyle 1996; Dunlap 1999; Morrison and Cohen 1999; and Cohn 2000). Small-scale die-offs of birds have been known at the Salton Sea since its early years, with nearly zoo individuals of various species found along the shore about December 1917 (Giltnan 1918). Recent massive die-offs of fish and birds (see, e.g., Saiki 1990; Jehl 1996; and Bruehler and de Peyster 1999) have caused alarm, particularly as they have occurred with increasing frequency and severity (Fig. 7), perhaps heralding a collapse of the ecosystem. Similar die-offs in the Gulf of California (Vidal and Gallo-Reynoso1996) suggest that problems exist on a broader scale, perhaps throughout the Salton Trough. Annual fish kills at the Salton Sea are thought to result from high concentrations of sulfide and ammonia at the bottom of

1940

1950

1960

1970

1980

1990

2000

Year F I G U R E 7. Bird d~e-offsat the Salton Sea since the mid1930s. Note that the severity and frequent). of mass rnortalities has Increased since the 1970s.

the sea mixing into surface water during the summer (Setmire et al. 1993). The causes of mass mortalities of birds are largely a matter of speculation, ranging from botulism to cholera to avian Newcastle disease (Kuiken 1999; Friend zooz), although botulism clearly is a principal culprit. Unfortunately, the environment of the Salton Sea favors botulism outbreaks, which are most likely to occur when low oxygen concentrations coincide with high water temperature and high salinity (Rockeand Samuel 1999). Recently five major ornithological societiesthe American Ornithologists' Union, the Association of Field Ornithologists, the Cooper Ornithological Society, the Western Field Ornithologists, and the Wilson Ornithological Society-adopted resolutions "in support of the Salton Sea as significant wildlife habitat" (see Condor 1oo:782-84; and Garrett 1998). CURRENT THREATS

Because the level of the Salton Sea is maintained by a balance between runoff from agricultural irrigation and evaporation, from the time of the sea's birth various chemicals and elements have become increasingly concentrated in its waters (Table I ) . High concentrations ofchemicals such as calcium and potassium may prove of little consequence to the long-term health of the Salton Sea ecosystem, whereas high concentrations of boron and sodium have been a cause for concern

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