1—
INTRODUCTION

The Hawaiian Crow (Corvus hawaiiensis), or 'Alala, is one of the most endangered birds in the world and faces likely extinction unless recovery actions begin soon. The only known wild population of this species is on private land, the 64,000-acre McCandless Ranch on the southwest slope of Mauna Loa in central Kona on the island of Hawai'i. The wild flock has been estimated recently to number 11 birds (J. Engbring, pers. comm., 1992). Little is known about the biology and life history of the few birds remaining. Because of concern about the most appropriate method to preserve the 'Alala, McCandless Ranch policy over the last decade has been to limit access to the crows by restricting entry onto the property. On the basis of trends in the overall population of the 'Alala in its historical range over the last 50 years, the U.S. Fish and Wildlife Service (USFWS) is of the opinion that the bird will become extinct unless appropriate actions are taken soon.

A captive-propagation program was established in 1976 and has been supported by the federal government and the state of Hawai'i. It was the first such program for any member of the corvid family, and it has met with some failures and some successes. The captive flock now consists of 10 bird—six that were bred and raised in captivity and four that were brought in from the wild. It is believed that the captive flock faces a severe genetic bottleneck: it produces fertile eggs each year, but very few chicks hatch. The low viability of eggs has been attributed by some biologists to inbreeding, disease, or unsatisfactory captive propagation techniques. Some captive-propagation specialists believe that genetic stock from the wild must be added to solve the problem; others disagree.

Because the 'Alala is on the endangered-species list, it is covered under the Endangered Species Act. Responsibility for implementation of recovery actions under the Endangered Species Act rests with USFWS. USFWS asked the National Research Council's Board on Biology to review available information on the 'Alala to determine the steps that would be appropriate to ensure the survival of the species. The committee on the Scientific Bases for the Preservation of the Hawaiian Crow—consisting of experts in ornithology, conservation biology, population biology, and captive propagation—was thereupon formed and charged to analyze the data and prepare a report detailing its findings, conclusions, and recommendations concerning the recovery of the 'Alala population. The committee and two special advisors examined the relevant scientific data, held a public meeting, and spoke to numerous persons, including state and federal biologists, staff at the captive-breeding facility at Olinda on the island of Maui, and



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Scientific Bases for the Preservation of the Hawaiian Crow 1— INTRODUCTION The Hawaiian Crow (Corvus hawaiiensis), or 'Alala, is one of the most endangered birds in the world and faces likely extinction unless recovery actions begin soon. The only known wild population of this species is on private land, the 64,000-acre McCandless Ranch on the southwest slope of Mauna Loa in central Kona on the island of Hawai'i. The wild flock has been estimated recently to number 11 birds (J. Engbring, pers. comm., 1992). Little is known about the biology and life history of the few birds remaining. Because of concern about the most appropriate method to preserve the 'Alala, McCandless Ranch policy over the last decade has been to limit access to the crows by restricting entry onto the property. On the basis of trends in the overall population of the 'Alala in its historical range over the last 50 years, the U.S. Fish and Wildlife Service (USFWS) is of the opinion that the bird will become extinct unless appropriate actions are taken soon. A captive-propagation program was established in 1976 and has been supported by the federal government and the state of Hawai'i. It was the first such program for any member of the corvid family, and it has met with some failures and some successes. The captive flock now consists of 10 bird—six that were bred and raised in captivity and four that were brought in from the wild. It is believed that the captive flock faces a severe genetic bottleneck: it produces fertile eggs each year, but very few chicks hatch. The low viability of eggs has been attributed by some biologists to inbreeding, disease, or unsatisfactory captive propagation techniques. Some captive-propagation specialists believe that genetic stock from the wild must be added to solve the problem; others disagree. Because the 'Alala is on the endangered-species list, it is covered under the Endangered Species Act. Responsibility for implementation of recovery actions under the Endangered Species Act rests with USFWS. USFWS asked the National Research Council's Board on Biology to review available information on the 'Alala to determine the steps that would be appropriate to ensure the survival of the species. The committee on the Scientific Bases for the Preservation of the Hawaiian Crow—consisting of experts in ornithology, conservation biology, population biology, and captive propagation—was thereupon formed and charged to analyze the data and prepare a report detailing its findings, conclusions, and recommendations concerning the recovery of the 'Alala population. The committee and two special advisors examined the relevant scientific data, held a public meeting, and spoke to numerous persons, including state and federal biologists, staff at the captive-breeding facility at Olinda on the island of Maui, and

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Scientific Bases for the Preservation of the Hawaiian Crow owners of the McCandless Ranch. The committee also visited the Olinda facility and spent 2 days on the McCandless Ranch. This report reflects the committee's analysis of all available information on the 'Alala. Chapter 2 summarizes what is known and identifies what is not known about the wild population. It includes a discussion of possible direct and indirect factors that have contributed to the decline of the 'Alala, a demographic analysis of the current wild population based on existing data, and an estimate of times to extinction of the 'Alala and other insular populations of corvid species. The demographic analysis revealed new information about the structure of the population. Chapter 3 discusses genetic considerations regarding small populations and their role in decision-making about the recovery of the 'Alala. Chapter 4 outlines the goals of a captive-breeding program, the history of the captive-breeding program for the 'Alala, and an analysis of the captive population's demography and genetics. Chapter 5 describes successes achieved in the reintroduction and translocation of other endangered species and presents evidence of reasons for optimism about the recovery of the 'Alala. Chapter 6 lays out eight options for the management of the two subpopulations of the 'Alala, and Chapter 7 describes the committee's major findings and recommendations.