The American Common Eider (Somateria mollisima dresseri) winters along the eastern coasts of the northern U.S. and southern Canada. Various lines of evidence indicate recent localized changes in eider abundance, particularly in the Gulf of Maine, where the most dramatic oceanic changes in the Northwest Atlantic are also underway. A range-wide overview of shifts in local abundance is needed to understand the geographic extent of changes in winter distribution, however, only the Canadian portion of their wintering range has been thoroughly and repeatedly surveyed by air in the last two decades (since 2003). We used these Canadian aerial survey data in combination with data from the Christmas Bird Count (CBC), a citizen science general bird census, to generate estimates of localized changes in abundance over a multi-decadal time series across the dresseri wintering range. CBC trends from the periods 1980–1999 and 2000–2020 were derived from negative binomial regressions and indicated an overall shift from mostly stable (λ = 1) or positive (λ > 1) localized trends in earlier years in the central region of the wintering range toward negative trends (λ < 1) in the most recent 20 years. Wintering numbers in Nova Scotia and the Bay of Fundy south through Maine showed the steepest shifts, where accelerating negative trends of λ = 0.85 - 0.95 have occurred since 2000. Many CBC sites in Massachusetts also shifted to negative trends, although a small number of sites from Cape Cod south have reported high counts in recent years resulting in locally high λ. Numbers in the far southern extent of the range also grew substantially, albeit with low numbers overall. CBCs at higher latitudes, in southeast Newfoundland and the Gulf of St. Lawrence, showed mostly stable or increasing trends. CBC coverage in the Canadian portion of the range is relatively poor, however, data from multiple years of aerial surveys in Canada corroborated CBC trends. The consistent and widespread nature of the declines in local abundance throughout the entire Gulf of Maine and surrounding ecosystems, from Nova Scotia to Massachusetts, suggests a large-scale redistribution away from the center of the overwinter range. Our confirmation of suspected spatial patterns in trends of American Common Eiders further supports the need for cross-jurisdictional coordination on the prioritization of harvest management and habitat conservation efforts among regions for this species.

The post Redistribution of wintering American Common Eiders (Somateria mollisima dresseri) first appeared on Avian Conservation and Ecology.

美国普通绒鸭 ( Somateria mollisima dresseri)）沿着美国北部和加拿大南部的东海岸过冬。各种证据表明最近绒鸭丰度发生了局部变化，特别是在缅因湾，西北大西洋最剧烈的海洋变化也正在发生。为了了解冬季分布变化的地理范围，需要对当地丰富度的变化进行全面的概述，然而，在过去二十年（自 2003 年以来）中，只有加拿大部分的越冬范围经过了彻底、反复的航空调查。我们将这些加拿大航空调查数据与公民科学一般鸟类普查圣诞鸟类计数 (CBC) 的数据结合使用，以生成德莱塞地区数十年时间序列中局部丰度变化的估计值越冬范围。1980-1999 年和 2000-2020 年期间的 CBC 趋势来自负二项式回归，表明越冬中部地区早期的局部趋势总体上从稳定 (λ = 1) 或正 (λ > 1) 趋势发生了整体转变最近 20 年呈负趋势 (λ < 1)。新斯科舍省和芬迪湾以南穿过缅因州的越冬数量显示出最陡峭的变化，自 2000 年以来出现了 λ = 0.85 - 0.95 的加速负趋势。马萨诸塞州的许多 CBC 站点也转向负趋势，尽管少数站点近年来，来自科德角以南的海龟计数较高，导致局部 λ 较高。尽管总体数量较少，但该山脉最南端的数量也大幅增长。高纬度地区的 CBC，在纽芬兰东南部和圣劳伦斯湾，大部分表现出稳定或增加的趋势。加拿大地区的 CBC 覆盖范围相对较差，但加拿大多年航空勘测的数据证实了 CBC 趋势。从新斯科舍省到马萨诸塞州，整个缅因湾和周边生态系统的局部丰度持续而广泛地下降，表明大规模的重新分布远离了越冬范围的中心。我们对美国绒鸭趋势中可疑的空间模式的确认进一步支持了跨辖区协调的必要性，以优先考虑该物种的收获管理和栖息地保护工作。加拿大地区的 CBC 覆盖范围相对较差，但加拿大多年航空勘测的数据证实了 CBC 趋势。从新斯科舍省到马萨诸塞州，整个缅因湾和周边生态系统的局部丰度持续而广泛地下降，表明大规模的重新分布远离了越冬范围的中心。我们对美国绒鸭趋势中可疑的空间模式的确认进一步支持了跨辖区协调的必要性，以优先考虑该物种的收获管理和栖息地保护工作。加拿大地区的 CBC 覆盖范围相对较差，但加拿大多年航空勘测的数据证实了 CBC 趋势。从新斯科舍省到马萨诸塞州，整个缅因湾和周边生态系统的局部丰度持续而广泛地下降，表明大规模的重新分布远离了越冬范围的中心。我们对美国绒鸭趋势中可疑的空间模式的确认进一步支持了跨辖区协调的必要性，以优先考虑该物种的收获管理和栖息地保护工作。从新斯科舍省到马萨诸塞州，整个缅因湾和周边生态系统的局部丰度持续而广泛地下降，表明大规模的重新分布远离了越冬范围的中心。我们对美国绒鸭趋势中可疑的空间模式的确认进一步支持了跨辖区协调的必要性，以优先考虑该物种的收获管理和栖息地保护工作。从新斯科舍省到马萨诸塞州，整个缅因湾和周边生态系统的局部丰度持续而广泛地下降，表明大规模的重新分布远离了越冬范围的中心。我们对美国绒鸭趋势中可疑的空间模式的确认进一步支持了跨辖区协调的必要性，以优先考虑该物种的收获管理和栖息地保护工作。

越冬的美国绒鸭 (Somateria mollisima dresseri) 的后重新分布首次出现在《鸟类保护与生态学》上。