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Severe declines of Eastern Imperial Eagle Aquila heliaca populations in the Baikal region, Russia: a modern and historical perspective

  • Vitaliy V. Ryabtsev (a1) and Todd E. Katzner (a2)
Abstract

The Eastern Imperial Eagle (Aquila heliaca), a vulnerable and declining species, is widely but sparsely distributed throughout its range. Because much of that range extends through the Russian-speaking world, relatively little on the species has been published in English. The world's easternmost population of Eastern Imperial Eagles, at Lake Baikal, Russia, is particularly well studied and, because of recent rapid population declines, is of great conservation concern. Here, using a data set covering more than 20 years evaluated in the context of historical accounts published in Russian, we assess recent severe declines in this population and the subsequent changes in its conservation status. In intensively surveyed areas near Lake Baikal, numbers of territories occupied by eagles have declined by 80–100% in the past 20–40 years. Likewise, throughout the entire region, the average number of known occupied and breeding territories were both more than 40% lower in 1998–1999 than they were in 1982–1983. These data suggest severe long-term declines in the population of Baikal's Imperial Eagles. Because we observed only limited decreases in reproductive output, our interpretation of the patterns in these data is that mortality of non-breeding birds (wintering adults and all pre-adults) is the most likely cause for this decline. Addressing the causes of this decline is critical to protect this severely threatened population from extirpation.

Восточный могильник (Aquila heliaca), уязвимый и сокращающийся в численности вид, широко, но разрозненно распространен по своему ареалу. В связи с тем, что большая часть его ареала находится в пределах русскоговорящей части мира, относительно мало опубликовано по этому виду на английском языке. Самая восточная группировка могильника находится в Прибайкалье. Она изучена особенно хорошо и из-за быстрого сокращения популяции вызывает особую тревогу и озабоченность природоохранников. Используя более чем >20 летние данные, рассмотренные в контексте исторических сведений опубликованных по-русски, мы оцениваем недавнее серьёзное сокращение этой популяции и последующие изменения в её природоохранном статусе. На территориях, находящихся под интенсивным обследованием в Прибайкалье, количество участков занятых орлами сократилось на 80–100% за последние 20–40 лет. Таким же образом, во всем регионе, среднее количество известных занятых территорий и гнездовых участков в 1998–1999 было на >40% меньше по сравнению с 1982–1983. Эти данные свидетельствуют о серьёзном долговременном сокращении прибайкальской популяции могильника. В связи с тем, что мы наблюдали лишь незначительное снижение результатов размножения, наша интерпретация модели по этим данным приводит к выводу, что смертность неразмножающихся птиц (зимующих взрослых и неполовозрелых птиц) является наиболее вероятной причиной этого сокращения. Выявление причин произошедшего падения численности очень важно для сохранения этой угрожаемой популяции от полного вымирания.

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Corresponding author
*Author for Russian-language correspondence. e-mail: vitryab@mail.ru or pr.bpark@inbox.ru
Author for English-language correspondence. e-mail: todd.katzner@aviary.org
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Bird Conservation International
  • ISSN: 0959-2709
  • EISSN: 1474-0001
  • URL: /core/journals/bird-conservation-international
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