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The Yellow-billed Loon, one of the rarest breeding birds in North America. Ryan Askren, USGS.
Why loons
From 2010 to 2014, the USGS Changing Arctic Ecosystems initiative focused on the Arctic Coastal Plain of northern Alaska, which has warmed quickly over the past 30 years, thawing permafrost and changing lakes and rivers. Loons depend on those lakes: they nest on freshwater lakes and eat the fish and invertebrates in them. They also live in the National Petroleum Reserve–Alaska, where oil and gas development is expected to grow. The USGS is studying how breeding loons use the lakes and how well they can adapt.
Three species
| Species | Nesting lakes | Status |
|---|---|---|
| Yellow-billed Loon | large, deep, connected lakes with fish all year | being considered for listing under the Endangered Species Act |
| Pacific Loon | smaller lakes that often freeze solid in winter, with fewer fish | stable or slightly increasing |
| Red-throated Loon | even smaller lakes; flies to the ocean to fish | fluctuates, perhaps with ocean conditions |
Pacific Loon. Ryan Askren, USGS.
Red-throated Loon. Ryan Askren, USGS.
The best nesting lakes have islands and peninsulas: they keep nests away from land predators such as foxes and offer sheltered shorelines.
Rivals
Loons are fiercely territorial, a sign that nest sites and food are limited. The big Yellow-billed Loon uses its size to drive the other two species off breeding lakes. The USGS has measured territory sizes to help set buffer zones around nests for industrial development. Warmer air will change lake levels and freezing, and with them fish, shorelines, and competition among the species.
An adult Yellow-billed Loon with a chick waits for the second egg to hatch. Ken Wright, USGS.
Winter journeys
Satellite tracking shows Yellow-billed Loons from the Coastal Plain migrate through the Bering Strait to winter off Asia, mostly near northern Japan. Yellow-billed and Red-throated loons have high yearly survival — above 90% — but birds wintering in Asia were more likely to carry elevated mercury and PCBs.
Migration routes of Yellow-billed Loons from Alaska's Arctic Coastal Plain to wintering areas in Alaska and Asia. USGS.
Mercury
Mercury is rising in Arctic fish-eating birds. Thawing permafrost and melting sea ice release natural mercury, and human sources likely add more. Most Yellow-billed Loons breeding in Alaska had blood mercury within natural background levels, but those wintering farther west in Asia had higher levels in their feathers. Comparing museum and modern samples shows about a two-fold increase over time.
Feather mercury in Yellow-billed Loons before 1920, in 1930–1950 and after 2000; black dots are averages. USGS.
Next
Research will look at how other environmental factors affect breeding, migration and the lakes loons use — their size, shape and fish — to forecast loon numbers and distribution as the Arctic warms, and to inform the Endangered Species Act decision on the Yellow-billed Loon.
Sources
Based on "Changing Arctic ecosystems: ecology of loons in a changing Arctic," U.S. Geological Survey Fact Sheet 2014–3093; a work of the United States government in the public domain. Photographs, map and chart are taken from the fact sheet's PDF. Research cited includes Haynes and others (2014) on nest sites and competition and Schmutz and others (2014) on territories.
Лицензия: CC0 1.0 (общественное достояние) · По материалам pubs.usgs.gov
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