The Great Thick-billed Murre Swimming Migration

A sense of wonder has stayed with me since seeing those Thick-billed Murre chicks jump at Prince Leopold Island on my first expedition cruise to Nunavut, as well as on subsequent trips until the most recent one in Aug. 2019. I have seen this also at the most northerly Canadian Thick-billed Murre colony on Coburg Island, at Cape Hay on Bylot Island, and at Akpait National Wildlife Area on the northeast side of Baffin Island. Akpait is the Inuktitut word for “murres.” Knowing about the life events that precede the youngsters’ awesome leaps help us appreciate why a fledgling undertakes this remarkable swimming migration with its male parent.

About three weeks before a young Thick-billed Murre jumps, it hatches from an egg laid on a high, narrow ledge crowded with neighboring Thick-billed Murres. Both male and female parents share rearing duties, their day divided into 12-hour shifts, one parent searching up to 100 km away for food, while the other keeps the chick warm and protected against marauding predators. As fledging time approaches, the male parent stays home more often and synchronizes his shift to be ready for the peak jumping time from 4pm to 2am, coinciding with the period of lowest light from late afternoon into the night. The midnight sun sets for the first time between Aug. 11 and 12.

At the time of fledging, the chick has grown to one quarter of the parent’s size and looks like a miniature adult, though its wings are not yet fully developed. A new coat of waterproof feathers has replaced fluffy down. Some chicks resemble adults in summer plumage, with a black chin and throat, while others resemble adults in winter plumage, having a white chin and white on the side of neck. The chick is small and fat, able to maintain its body temperature well enough to survive in cold Arctic waters.

Thick-billed Murre chicks undertake the great swimming migration with their fathers. Researchers are not sure why chicks are accompanied by their fathers and not their mothers. Photo by © Jean Iron.

Together, father and chick undertake a remarkable swimming migration to their wintering grounds off the west coast of Greenland, far from the natal cliffs of Prince Leopold Island. Using the low light of their first night, they swim as far from the colony as possible to evade aerial predators such as Glaucous Gulls. The ocean currents help them as they move rapidly eastward in Lancaster Sound, then south in Baffin Bay. They have little more than a month to swim out of Lancaster Sound to avoid being trapped by ice, which may form as early as October.

For the first five to six weeks, the chick cannot fly or find its own food. Yet, it grows strong while being fed by its male parent. At this time, for several weeks, the adult is also flightless while molting all its flight feathers synchronously as part of the complete molt into winter plumage. Father and young stay together until the young can fly and hunt its own food. This incredible feat of long-distance migration by a young bird occurs while it is still unable to fly and not yet fully developed.

I asked Thick-billed Murre researcher Anthony Gaston why the male and not the female accompanies the young. He said the reason is not known. One theory is the female puts more effort into feeding the young in the later stage of its growth on the ledge and needs a break. After the young fledge, females take off on their own southbound migration.

The pressures of a brief Arctic breeding season, an unpredictable environment, and the tremendous energy involved in adults feeding young have likely contributed to the short time from chick hatching to fledging. The youngsters finish growing while swimming to their wintering grounds south of the pack ice. These young Thick-billed Murres remain at sea for the next two to three years before returning to Prince Leopold Island, where lucky observers may have the chance to glimpse these remarkable birds begin the great swimming migration again. 

To learn more about Thick-billed Murres, their swimming migration, or the birds of the Canadian Arctic, check out these books. 

Acknowledgments

Anthony Gaston has researched Thick-billed Murres in the Canadian Arctic for over 45 years and written extensively about them. I thank him for information and for answering my questions. I am grateful to Quest Nature Tours of Toronto for opportunities to visit Nunavut in the Canadian High Arctic and share these magnificent seabirds with others.

Jean Iron is a well-known Ontario birder, a former president of Ontario Field Ornithologists, and recipient of their Distinguished Ornithologist Award. Jean has a passion for Arctic birds, and, as an expedition leader for Quest Nature Tours to Canada’s High Arctic, she has observed Thick-billed Murres many times at their nest cliffs.