Long-term decline and geographical variation in the numbers of moulting Common Eiders Somateria mollissima in Shetland

IF 0.7 4区生物学 Q3 ORNITHOLOGY

Bird Study Pub Date : 2021-10-02 DOI:10.1080/00063657.2022.2141192

Will T. S. Miles, M. Mellor, S. Gear, P. Harvey, G. Tyler

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引用次数: 0

Abstract

ABSTRACT Capsule: Numbers of moulting Common Eiders Somateria mollissima counted in Shetland during surveys from 1977 to 2019 decreased from approximately 14,500 to an estimated 3600 individuals, a 75% population decline. Aims: To report results of extensive surveys of Eiders across Shetland during the annual complete moult period, review historical surveys, and evaluate long-term population changes and the possible underlying causes for change. Methods: Extensive areas of coastal Shetland were surveyed for Eiders during the annual moult period from July to September, every one to five years from 1977 to 2019. Spatial sampling was variable between surveys from 1977 to 1993 but more systematic and standardised during all surveys from 1996 to 2019. Overall population change, changes in numbers of birds within areas categorised as either exposed or sheltered coast, and change in the proportion of adult males to females/juveniles were assessed. Results: Surveys from 1977 to 1993 indicated a 55% decrease, from approximately 14,500–6500 individuals, and surveys from 1996 to 2019 showed a 45% decrease, from an estimated 6700–3600 individuals, indicating an overall population decrease of approximately 75% from 1977 to 2019. From 1996 to 2019, Eider numbers decreased in areas of exposed coast by approximately 90% but increased by at least 70% in the more sparsely populated sheltered areas, and the overall proportion of adult males to females/juveniles reduced by one-third. Conclusion: From 1977 to 2019, a substantial decline of approximately 75% occurred in the Shetland Eider population at the time of moult. Shetland Eiders are not S. m. mollissima but morphologically and genetically akin to S. m. faeroeensis, the Faroese subspecies, the rarest subspecies worldwide, so this decline is of high conservation concern. Causes of the decline largely remain unknown, but ecological datasets on Shetland Eiders are few and detailed studies, including remote tracking of individuals’ movements throughout the year, would be worthwhile.

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设得兰岛蜕皮公鸭数量的长期下降和地理变异

摘要:在1977年至2019年的调查中，设得兰群岛的换羽普通绒鸭(Somateria mollissima)的数量从约14,500只下降到约3,600只，种群数量下降了75%。目的:报告在年度完全换羽期对设得兰群岛的艾德鸭进行的广泛调查的结果，回顾历史调查，并评估长期的种群变化和可能的潜在变化原因。方法:1977 - 2019年，在每年7 - 9月的换羽期，每1 - 5年对设得兰沿海广大地区进行调查。在1977年至1993年的调查中，空间抽样是可变的，但在1996年至2019年的所有调查中，空间抽样更加系统化和标准化。评估了总体种群变化、在暴露海岸或隐蔽海岸区域内鸟类数量的变化，以及成年雄性与雌性/幼鸟比例的变化。结果:从1977年到1993年的调查显示，从大约14500 - 6500只下降了55%，从1996年到2019年的调查显示，从估计的6700-3600只下降了45%，表明从1977年到2019年，总人口减少了大约75%。从1996年到2019年，裸露海岸地区的绒鸭数量减少了约90%，但在人口较少的庇护地区，绒鸭数量增加了至少70%，成年雄性与雌性/幼鸟的总体比例减少了三分之一。结论:从1977年到2019年，设得兰绒鸭换羽时的种群数量大幅下降了约75%。设得兰绒鸭不是S. m. mollissima，但在形态和遗传上与S. m. faeroeensis(法罗亚种，世界上最稀有的亚种)相似，因此这种下降受到高度关注。数量减少的原因大部分仍不清楚，但设得兰绒鸭的生态数据很少，详细的研究，包括全年对个体活动的远程跟踪，将是值得的。

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来源期刊

Bird Study 生物-鸟类学

CiteScore

1.60

自引率

0.00%

发文量

审稿时长

6-12 weeks

期刊介绍： Bird Study publishes high quality papers relevant to the sphere of interest of the British Trust for Ornithology: broadly defined as field ornithology; especially when related to evidence-based bird conservation. Papers are especially welcome on: patterns of distribution and abundance, movements, habitat preferences, developing field census methods, ringing and other techniques for marking and tracking birds. Bird Study concentrates on birds that occur in the Western Palearctic. This includes research on their biology outside of the Western Palearctic, for example on wintering grounds in Africa. Bird Study also welcomes papers from any part of the world if they are of general interest to the broad areas of investigation outlined above. Bird Study publishes the following types of articles: -Original research papers of any length -Short original research papers (less than 2500 words in length) -Scientific reviews -Forum articles covering general ornithological issues, including non-scientific ones -Short feedback articles that make scientific criticisms of papers published recently in the Journal.