International migration patterns of Red-throated Loons (Gavia stellata) from four breeding populations in Alaska

Abstract

Identifying post-breeding migration and wintering distributions of migratory birds is important for understanding factors that may drive population dynamics. Red-throated Loons (Gavia stellata) are widely distributed across Alaska and currently have varying population trends, including some populations with recent periods of decline. To investigate population differentiation and the location of migration pathways and wintering areas, which may inform population trend patterns, we used satellite transmitters (n = 32) to describe migration patterns of four geographically separate breeding populations of Red-throated Loons in Alaska. On average (± SD) Red-throated Loons underwent long (6,288 ± 1,825 km) fall and spring migrations predominantly along coastlines. The most northern population (Arctic Coastal Plain) migrated westward to East Asia and traveled approximately 2,000 km farther to wintering sites than the three more southerly populations (Seward Peninsula, Yukon-Kuskokwim Delta, and Copper River Delta) which migrated south along the Pacific coast of North America. These migration paths are consistent with the hypothesis that Red-throated Loons from the Arctic Coastal Plain are exposed to contaminants in East Asia. The three more southerly breeding populations demonstrated a chain migration pattern in which the more northerly breeding populations generally wintered in more northerly latitudes. Collectively, the migration paths observed in this study demonstrate that some geographically distinct breeding populations overlap in wintering distribution while others use highly different wintering areas. Red-throated Loon population trends in Alaska may therefore be driven by a wide range of effects throughout the annual cycle.

The diet of red-throated divers (Gavia stellata) overwintering in the German Bight (North Sea) analysed using molecular diagnostics

“…Red-throated divers are medium sized birds with weight varying between 1400g -2000g (own observations), and with high wing loading (Storer 1958;Lovvorn and Jones 1994). Despite this, these birds often need to cover long distances to their breeding grounds (www.divertracking.com;McCloskey et al 2018), with some individuals travelling as far as 850km or 1300km in a single flight (Kleinschmidt et al unpubl data). Weber et al (1997) Diet composition of red-throated divers in the German Bight showed the importance of resting sites for refuelling.…”

Loon abundance and behaviour over four decades at a remote ecological reserve on Haida Gwaii, British Columbia, Canada

“…In the Baltic Sea, northern Europe, an important overwintering habitat of aquatic birds, there was an 85% reduction of Red-throated Loon and Arctic Loon (Gavia arctica) from 1987 to 2000 (Skov et al 2011), declines generally considered to originate from increased mortality in marine habitats (Schmutz 2014), but also from ecological disturbance to nesting ponds in Swedish populations (Eriksson 1994). Red-throated Loon from Haida Gwaii are thought to overwinter on inshore marine waters in southern British Columbia (Campbell et al 1990) and possibly further south, as recent satellite-tracking of Alaskan birds (McCloskey et al 2018) indicates that some adults overwinter in coastal waters of Mexico. Inshore habitats impose the highest risk to overwintering seabirds (Croxall et al 2012).…”

Technology wish lists and the significance of temperature-sensing wildlife telemetry

“…After nearly a century of telemetry innovation, there is now a wide array of telemetry devices with an even wider array of potential applications [1,2,12,16]. Telemetry now enables studies on topics such as animal movement and migration [17][18][19], physiological processes [20,21], or social interactions [22], and our survey respondents compiled an even longer list of current applications (Additional file 2). However, the survey responses also show how many research interests still cannot yet be satisfactorily investigated using telemetry.…”