Common Loons are Faithful to Wintering Sites

Researchers have long known that loons throughout Canada and the northern United States stay faithful to their spring nesting sites, however, new research shows for the first time that the birds are also faithful to their wintering sites.

“There isn’t much winter ecology research that’s been done,” said James Paruk, the senior scientist at the Biodiversity Research Institute, a non-profit organization that uses scientific findings to advance awareness and inform decision-makers. “Because of this, there are some gaps in our knowledge.”

Paruk, who has studied loons for about two decades, is also the lead author of the new study on loons’ wintering habits, recently published in The Condor: Ornithological Applications.

The main reason for this paucity of data is that winters pose a challenge for researchers studying common loons, Paruk said. The birds have molted their striking black and white breeding plumage for their uniformly gray and dull winter plumage and as such are easily overlooked. In addition, in the ocean they can be miles from shore, outside of the range of most binoculars and spotting scopes.

Paruk and his research team began studying loon winter ecology in 2004 in Morro Bay, California, and later expanded to Louisiana and an inland reservoir in Washington. Most recently, researchers tagged common loons in Maine with satellite transmitters to track their winter range. Each captured loon was given a unique color band combination, which would identify it in future years. They found loons had a high likelihood of returning to the same wintering sites each year.

The results of this study have important implications for conservationists, especially since some of these wintering areas have been impacted greatly by the BP oil spill of 2010. “When [the loons] return to a contaminated site year after year, to me it speaks volumes for why we have to clean up these areas as quickly and thoroughly as possible,” Paruk said. “Birds in wintering areas might get exposed to oil annually. This is important to their survivorship and reproductive success.”

Paruk hopes to further study common loons including how their genetics plays a role in their migration. For example, in Minnesota, some loons winter in the Atlantic and some winter in the Gulf of Mexico. Paruk wants to find out if it is possible wintering site preferences are passed on through genetics. “This [study] opens the door for more potential research,” Paruk said. “Now we know they come back to the same area. There are many other things to consider.”

Header Image: A common loon in the process of molting its feathers is unable to fly. In a recently published study, researchers found that common loons often return to the same winter nest sites each year.

Image Credit: D. Long, IV