Black-throated blue warbler (Setophaga caerulescens) populations have been declining at the southern edge of the breeding range in North Carolina over the past two decades. Determining the causes of population declines in migratory species requires knowledge of the threats faced throughout the entire annual cycle, necessitating accurate information about the migratory routes and non-breeding areas used by birds. We used light-level geolocators to identify the fall migratory routes and non-breeding distributions of adults breeding at the southern edge of the range in North Carolina (n = 5), where populations are declining, and at the core of the range in New Hampshire (n = 8), where populations are stable. The strength of migratory connectivity was moderate (mean = 0.42). New Hampshire birds used non-breeding areas broadly distributed across the Caribbean, whereas North Carolina birds used a restricted non-breeding area largely in the Dominican Republic. Suitable forest cover declined at a higher rate from 2000 to 2019 in the Dominican Republic than in other Caribbean countries (8.4% vs. 2–4% loss), exposing birds from the trailing edge to significantly higher suitable habitat loss on the non-breeding grounds compared with range-core birds. Birds from the two study populations also exhibited differing migratory routes, with North Carolina birds migrating south through Florida and many New Hampshire birds performing an overwater flight from the Carolinas to the Caribbean. Our results suggest the possibility that, at least for this species, forest loss on the island of Hispaniola could be exacerbating population declines at the southern edge of the breeding range in North Carolina.

The post Light-level geolocation reveals moderate levels of migratory connectivity for declining and stable populations of Black-throated Blue Warblers (Setophaga caerulescens) first appeared on Avian Conservation and Ecology.

过去二十年来，北卡罗来纳州繁殖地南部边缘的黑喉蓝莺（Setophaga caerulescens ）数量一直在下降。确定迁徙物种数量下降的原因需要了解整个年度周期中面临的威胁，需要有关鸟类迁徙路线和非繁殖区的准确信息。我们使用光级地理定位器来确定在北卡罗来纳州范围南部边缘（n = 5）繁殖的成虫的秋季迁徙路线和非繁殖分布，那里的种群数量正在下降，并且位于新州范围的核心。汉普郡 ( n = 8)，人口稳定。迁移连接的强度中等（平均值 = 0.42）。新罕布什尔州的鸟类使用广泛分布在加勒比地区的非繁殖区，而北卡罗来纳州的鸟类则主要使用多米尼加共和国的有限非繁殖区。从 2000 年到 2019 年，多米尼加共和国的适宜森林覆盖率下降速度高于其他加勒比国家（下降 8.4% 对 2-4%），使后缘的鸟类在非繁殖地遭受明显更高的适宜栖息地丧失与范围核心鸟类相比。来自两个研究种群的鸟类也表现出不同的迁徙路线，北卡罗来纳州的鸟类通过佛罗里达州向南迁徙，许多新罕布什尔州的鸟类从卡罗来纳州到加勒比海进行水上飞行。我们的研究结果表明，至少对于该物种而言，伊斯帕尼奥拉岛上的森林丧失可能会加剧北卡罗来纳州繁殖范围南缘的种群数量下降。

光级后的地理定位揭示了黑喉蓝莺（Setophaga caerulescens）数量下降和稳定的中等水平的迁徙连通性，首次出现在《鸟类保护与生态学》上。