by Frank Keim
original artwork by Frank Keim
Like their lookalike first cousins, the tuxedo-clad Common murres, Thick-billed murres are among the deepest divers of all birds, sometimes foraging for their food as deep as 670 feet. This is about 100 feet deeper than Common murres. Also, like their cousins, they nest in large colonies on high rocky sea cliffs of islands and headlands in the Bering Sea. Often breeding shoulder to shoulder on those cliffs, they may hold the world record for needing the least personal space among birds. They also live long lives, up to almost 29 years, and often mate for life.
During the breeding season, they prefer to forage near the edge of sea ice and also in places where the shape of the land and strong seawater currents focus their prey. Where their range overlaps with the Common murre, Thick-bills search for their food farther from shore in deeper waters. At other times of the year, they spend most of their time on the ocean, and often winter in pack ice, where large openings provide access to their prey.
Like other members of the auk family, Thick-billed murres eat mostly small fish, squid, shrimp, and crustaceans. During their deepwater dives, they forage alone or in flocks at or near the sea floor and catch prey with their bill. Although they are awkward walkers on land, they are swift agile swimmers underwater. Using their wings for propulsion and their feet for steering, they are as graceful as swallows as they “fly” after their prey.
Unless delivering the food to their single chick, they usually consume it underwater. Their preferred fish species include: walleye Pollock, Arctic cod, Atka mackerel, capelin, Pacific herring, sandlance, sculpin, blenny, lumpsucker, and lanternfish. I mention this because many of these species, if not all of them, are becoming increasingly more scarce because of the warming waters of the Bering Sea caused by climate heating.
As with other auk species, these murres do not breed until they’re four years old. One-year-old birds remain at sea and don’t visit nesting areas at all. Two-year-olds fly in flocks in circles above the colony, checking out potential mates and landing briefly as if to announce their interest in what’s going on. During their third year, they gather at the top of the nest cliff and seriously socialize with others of their age, preening each other and forming bonds to carry them through what could be a life-long relationship. Finally in their fourth year they are ready to get down to business and have their first family, which amounts to only one chick.
Some of their courting rituals include mutual preening at the nest site, pair-bowing, nibbling at each other’s bills, and presenting pebbles to each other. They may also jump off the cliff and do a slow wing-flutter as they descend from a nesting ledge, then chase at each other madly across the sea surface. When the birds finally decide to nest they find a flat ledge on a rocky cliff, arrange a rough pile of pebbles or other debris around the site where the single egg will be laid, then cement them in place with their guano. The egg is pointed at one end to keep it from rolling over the edge of the cliff. Its color ranges from white to tan to dark green or turquoise with or without black splotches.
Incubation is by both parents for 30-35 days, and one of them is almost always at the nest throughout the nesting cycle. It must get rather cozy while incubating because Alpak nest closer together than any other colonial birds, even touching each other as they brood their individual eggs.
When the egg hatches, the young bird is covered in down and able to stand within one day. Both parents help feed the chick, and, again, one bird is always present as the other hunts at sea or rests on the water below the nest ledge. When feeding their young, they may travel over 100 miles on foraging flights, usually in flocks and following a leader on a direct course to and from the feeding area just to bring back one fish at a time for their chick.
After 15-30 days in the nest, and even before the young can fly, it plunges over the nest ledge and glides and flutters down to the surface of the sea, accompanied by its father who will feed the young bird and help it learn how and where to forage until it becomes fully independent and can fly several weeks later. Although the mother bird’s job is done, she often remains in the colony for several weeks thereafter. After their single child has fledged, Thick-billed murres generally forage at sea alone during the winter months, but they will gather in large flocks where prey is abundant and often congregate on floating ice when not foraging.
Thick-billed and Common murres resemble each other so closely the coastal people refer to them both by the same Yup’ik name, Alpak (also Alpa), which may refer to the way they emerge so suddenly like a dart from the surface after their rapid ascent from their deep dives underwater. Their scientific name, Uria lomvia, means “diving auk,” from the Greek word, ourien, “to dive,” and Swedish, lomvia, meaning “auk.” As with the Common murre, their English name is imitative of the murmuring sound they make at their rookeries. They have a thicker bill than Common murres do.
Alpak are still numerous throughout their circumboreal range. However, they have lost population everywhere due to oil spills, heavy metal and pesticide poisoning as well as entanglement in fishing gear. Warmer ocean waters due to climate heating are also causing major declines in their prey resources at all times of the year, so this could soon lead to a serious reduction in their numbers worldwide.
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