Standard waterfowl molt drives were successfully used to capture molting male common mergansers. Photo: Denny Zwiefelhofer/USFWS

Captured birds are carefully processed and released. Pictured are (left to right): Denny Zwiefelhofer (Kodiak Refuge), Nate Maryanski (Kodiak Refuge), and John Pearce (USGS) holding a captured merganser duck. Photo: Brandon Saito/USFWS

According to a recent study, it appears that Kodiak Island may be “the place to be” if you are a molting male merganser. Led by Dr. John Pearce of the U.S. Geologic Survey Alaska Science Center and supported by the Sea Duck Joint Venture and Kodiak National Wildlife Refuge, the study was the first to document that male common mergansers molting on Kodiak Island originate from a wide variety of locations besides southcentral Alaska including interior and western Alaska, the Aleutian Islands, Russia, and the Pacific Northwest.

Typically, within a few weeks after breeding, ducks and geese undergo a complete molt of their flight feathers, in other words, they lose their primary wing feathers, becoming flightless for a time, until they grow in a new set of flight feathers. In this way they ensure that their flight feathers never wear out – sort of like an annual tire change. Breeding females usually remain with their young and molt in the vicinity of their breeding area. Males, however, often abandon their mates after breeding and travel to traditional molting areas where they sometimes gather in sizeable groups with males from other areas.

By banding birds and analyzing DNA from feathers, Dr. Pierce’s study sought to determine whether the same molting birds return to Kodiak each year and from where the birds had originated. This was the third year of capturing molting birds on Karluk Lake, and this year, in addition, captures were made on Frazer Lake and on Uyak, Terror, and Uganik Bays. In 2006, 9 of 53 birds caught on Karluk Lake had been captured and banded at Karluk in 2005. This year, 2 of 39 birds caught at Karluk were recaptures from 2005. This indicates that a good portion of the males molting on Karluk Lake in past years have returned to Karluk to molt. Preliminary analysis of DNA from 67 common mergansers caught at Kodiak’s Karluk Lake in 2005 and 2006 indicated that most (42) were born in southcentral Alaska (Cordova, Kenai Peninsula, Anchorage, Kodiak), 15 were born in various northern and western locales (Fairbanks, Togiak, Aleutians, eastern Russia), but 10 were born as far south as the Pacific Northwest (Washington, Oregon, and northern California). Biologists have previously documented far-flung dispersal of molting male sea ducks of a few other species but not in common merganser.