Conservation Status and Threats
Although the Red-throated Loon is not a globally threatened species, as it has a large population and a significant range, there are populations which appear to be declining. Numbers counted in U.S. Fish and Wildlife Service surveys in Alaska show a 53 percent population decline between 1971 and 1993, for example, and counts have dropped in continental Europe as well. In Scotland, on the other hand, the population increased by some 16 percent between 1994 and 2006, according to surveys done by the Royal Society for the Protection of Birds and Scottish Natural Heritage. In 2002, Wetlands International estimated a global population of 490,000 to 1,500,000 individuals; global population trends have not been quantified.
The Red-throated Loon is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies; in the Americas, it is protected by the Migratory Bird Treaty Act of 1918. Oil spills, habitat degradation, and fishing nets are among the main threats this species faces. Because it tends to migrate close to shore—generally within 20 kilometres (12 mi) of land—it may be detrimentally affected by the construction of near-shore wind farms; studies indicate a high level of avoidance of wind farm areas, though deaths due to direct strikes with the turbines appear to be uncommon. High levels of mercury in the environment have led to reproductive failures in some areas, including parts of Sweden. Studies in Sweden have also shown that they may be adversely impacted by the acidification of lakes, as the fish on which they prey are susceptible to low pH. On the breeding grounds, Arctic and Red Foxes are major predators of eggs, while Great Skuas, Arctic Skuas and various species of Larus gulls (including Great Black-backed Gulls and Glaucous Gulls) are predators of both eggs and young.
The species is known to serve as host for at least 51 species of parasites, most of which are roundworms (nematodes), flatworms (digeneans) and tapeworms (cestodes) carried internally; a single species of louse is its only known external parasite. It is also known to sometimes carry significant populations of diatoms (microscopic phytoplankton) on its contour feathers. The Red-throated Loon is susceptible to avian influenza and Type E botulism, and is regularly killed by the ingestion of neurotoxins produced by "red tide" algal blooms. During a 2007 bloom, large numbers of the birds also died of hypothermia, after their plumages became matted by a protein byproduct of the algae, which reduced the insulating properties of their feathers.
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