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NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. In preparing its report, the committee invited people with different perspectives to present their views. Such invitation does not imply endorsement of those views.
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This study by the National Research Council's Commission on Life Sciences was sponsored by the US Department of the Interior Fish and Wildlife Service under cooperative agreement no. 14-0001-48-96520. Points of view in this document are those of the authors and do not necessarily represent the official position of the US Department of the Interior.
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COMMITTEE ON THE SCIENTIFIC BASES FOR THE PRESERVATION OF THE MARIANA CROW
W. DONALD DUCKWORTH, Chair,
Bishop Museum, Honolulu, Hawaii
STEVEN R. BEISSINGER,
University of California, Berkeley
SCOTT R. DERRICKSON,
National Zoological Park, Front Royal, Virginia
THOMAS H. FRITTS,
National Biological Service, Washington, DC
SUSAN M. HAIG,
Oregon State University, Corvallis
FRANCES C. JAMES,
Florida State University, Tallahassee
JOHN M. MARZLUFF,
Sustainable Ecosystems Institute, Meridian, Idaho
BRUCE A. RIDEOUT,
Center for Reproduction of Endangered Species, San Diego, California
NRC Staff
ERIC A. FISCHER, Board Director
TANIA WILLIAMS, Study Director
PAULETTE A. ADAMS, Project Assistant
JEFFREY PECK, Project Assistant
BOARD ON BIOLOGY
MICHAEL T. CLEGG, Chair,
University of California, Riverside, California
JOHN C. AVISE,
University of Georgia, Athens
DAVID EISENBERG,
University of California, Los Angeles
GERALD D. FISCHBACH,
Harvard Medical School, Cambridge, Massachusetts
DAVID J. GALAS,
Darwin Technologies, Seattle, Washington
DAVID V. GOEDDEL,
Tularik, Inc., San Francisco, California
ARTURO GOMEZ-POMPA,
University of California, Riverside
COREY S. GOODMAN,
University of California, Berkeley
BRUCE R. LEVIN,
Emory University, Atlanta, Georgia
OLGA F. LINARES,
Smithsonian Tropical Research Institute, Miami, Florida
ELLIOTT M. MEYEROWITZ,
California Institute of Technology, Pasadena
ROBERT T. PAINE,
University of Washington, Seattle
RONALD R. SEDEROFF,
North Carolina State University, Raleigh
DANIEL SIMBERLOFF,
Florida State University, Tallahassee
ROBERT R. SOKAL,
State University of New York, Stony Brook
SHIRLEY M. TILGHMAN,
Princeton University, Princeton, New Jersey
RAYMOND L. WHITE,
University of Utah, Salt Lake City
Staff:
ERIC FISCHER, Director
KATHLEEN BEIL, Administrative Assistant
JANET JOY, Program Officer
JEFFREY PECK, Project Assistant
TANIA WILLIAMS, Program Officer
COMMISSION ON LIFE SCIENCES
THOMAS D. POLLARD, Chair,
Johns Hopkins University, Baltimore, Maryland
FREDERICK R. ANDERSON,
Cadwalader, Wickersham & Taft, Washington, DC
JOHN C. BAILAR III,
University of Chicago, Illinois
JOHN E. BURRIS,
Marine Biological Laboratory, Woods Hole, Massachusetts
MICHAEL T. CLEGG,
University of California, Riverside
GLENN A. CROSBY,
Washington State University, Pullman
URSULA W. GOODENOUGH,
Washington University, St. Louis, Missouri
SUSAN E. LEEMAN,
Boston University, Massachusetts
RICHARD E. LENSKI,
Michigan State University, East Lansing
THOMAS E. LOVEJOY,
Smithsonian Institution, Washington, DC
DONALD R. MATTISON,
University of Pittsburgh, Pennsylvania
JOSEPH E. MURRAY,
Wellesley Hills, Massachusetts
EDWARD E. PENHOET,
Chiron Corporation, Emeryville, California
EMIL A. PFITZER,
Research Institute for Fragrance Materials Inc., Hackensack, New Jersey
MALCOLM C. PIKE,
University of Southern California, Los Angeles
HENRY C. PITOT, III,
University of Wisconsin, Madison
JONATHAN M. SAMET,
Johns Hopkins University, Baltimore, Maryland
HAROLD M. SCHMECK JR,
32 Seapine Road, North Chatham, Massachusetts
CARLA J. SHATZ,
University of California, Berkeley
JOHN L. VANDEBERG,
Southwest Foundation for Biomedical Research, San Antonio, Texas
Staff:
PAUL GILMAN, Executive Director
SOLVEIG PADILLA, Administrative Assistant
Preface
The unique and fragile nature of environments found in oceanic island systems is well known. Through colonization and evolution, these relatively small land areas have evolved unique biota characterized by small populations, rare forms, and low phylogenetic diversity. They are also exceedingly vulnerable to human disturbance and to invasions of introduced species. Thus, while this report focuses on the challenges posed by preserving one species, the aga (or Mariana crow), it reflects the larger issues and challenges of biodiversity conservation in all oceanic island ecosystems.
The Mariana archipelago is the most northerly island group in Micronesia, lying roughly equidistant from Japan to the north, New Guinea to the south, and the Philippines to the west. Consisting of a north-south chain of 15 islands that extends over 675 km, the Marianas are in reality the emergent portions of a mighty mountain range that rises from the deepest portion of the Pacific Ocean, the Mariana Trench. The islands are volcanic in origin and generally diminish in size from south to north. The warm humid climate is distinguished by relatively constant temperature, wet and dry seasons, and a high annual probability of typhoons during the wet season.
The native ecosystems of the archipelago have been in decline since the earliest colonization by humans. Habitat destruction and alteration have been especially severe during this century as a result of war, post-war development, and associated intentional or accidental introduction of predatory or competitive species, especially on Guam. While these factors have impacted all groups of native organisms in the Mariana Islands to one degree or another, the extinction or near extinction of nearly all the native forest birds on Guam, most certainly linked to
the large population of the introduced brown tree snake, is by far the most significant and alarming. The rapid decline of the aga is another painful reminder of the importance and challenge of preserving the unique environmental heritage of these islands, the need for increased knowledge to restore and maintain native species and habitats, and the compelling and lasting value of extensive public education to stimulate environmentally informed public policy development.
In response to a request from the US Fish and Wildlife Service (FWS), the National Research Council's Board on Biology established the Committee on the Scientific Bases for the Preservation of the Mariana Crow (aga) in March 1996. Its task was to review the existing data pertaining to the aga while focusing on several scientific issues:
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Assess to the extent possible the causes of the continuing decline in populations of the aga in the wild;
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Evaluate options for action to halt or reverse the decrease in numbers of the aga;
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Estimate the minimum viable population for survival of the Guam population of this species; and
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Evaluate the advisability of adding genetic material from the Rota population to the Guam population.
Current options for the recovery of the aga populations vary; they range from continuing present management strategies to a variety of translocations of one or both populations. From the assembled data and their evaluation, the committee has developed a set of recommendations designed to assist interested parties in working effectively to aid the recovery of the aga.
The committee held three meetings: one in Hawaii (Honolulu, April 1996); one in Guam and Rota (May 1996); and one at the Arnold and Mabel Beckman Center in Irvine, California (June 1996). The committee collected and reviewed data on the aga from biologists in federal, state, territorial, and commonwealth agencies, and other scientists and individuals. Members visited the 'alala (Hawaiian crow) recovery project on the island of Hawaii during the first meeting, and we are grateful to Cynthia Salley, McCandless Ranch, the FWS, and the Peregrine Fund for facilitating that opportunity. In Guam, the committee visited the laboratories and rearing facilities of both federal and Guam agencies and was extensively briefed both in field locations and formal settings. On Rota, nesting sites were observed and a broad range of aga habitat was visited through the support and generosity of Stan Taisacan of the Commonwealth of the Northern Mariana Islands Department of Lands and Natural Resources Division of Fish and Wildlife, and Dan Grout of FWS. The information and support provided by those people and many others were invaluable to the committee and to the development of this report. In addition, we are grateful to the many other persons and organizations who assisted the committee in preparing this report (See appendix B).
From the outset of this study, the committee has been constantly motivated to produce a report in a time-frame that would allow for consideration of its recommendations by the FWS and related agencies for implementation during this year's breeding season. Consequently, the committee schedule was fast-paced and intensive, but never at the expense of limiting the fullest measure of discussion and evaluation of available data in reaching consensus. It was my pleasure and privilege to work with a talented, enthusiastic, and dedicated committee. This report is the product of their hard work and spirited, yet always collegial, debate. I want to express my deepest gratitude for their patience, their insight, and their generosity in response to the rigorous schedule and scientific challenges imposed by the task.
Last, on behalf of the entire committee, I want to express our gratitude to the National Research Council staff for the vital role they played in all aspects of the study. The dedication and persistence of project director Tania Williams facilitated and expedited the committee's activities throughout the study. In addition, Paulette Adams and Jeff Peck provided support for our various activities.
W. Donald Duckworth, Chair
Committee on the Scientific Bases for the Preservation of the Mariana Crow
September 1996