Scientific name: Uria lomvia
Danish: Kortnaebet Lomvie
English: Brunnich's Guillemot
Greenland: Agpa
Japanese: Hashibuto Umigarasu
Russian: Gaharka
St. Lawrence Island: Kuwok; Athlpa

Practically all that has been said about the Common Murre also applies to the Thick-billed Murre, although the latter is more northerly in its breeding range. Thick-bills are truly birds of the Arctic marine zone and one of the most populous species of the cold, northern oceans. From the coasts of the Eastern Siberian Islands south to the Kuriles, Pribilofs, Aleutians, Shumagins, and other islands, the birds range into the Pacific, and casually to British Columbia in the winter. On the Atlantic side, Thick-bills occupy huge colonies or bazaars north of the Soviet Union and Norway to Iceland, Greenland, and the coastal areas of Labrador and northern Canada. Their breeding range there extends south to Newfoundland where they mix on island colonies with the Thin-bills on Green Islands in Witless Bay and at Cape St. Mary's. Bird Rocks and Magdalen Islands in the St. Lawrence Estuary also harbor small colonies. Comprehensive, breeding ecology studies of this species on Prince Leopold Island of Canada's high arctic have been presented by A.J. Gaston and D.N. Nettleship.²¹⁰

Early estimates have suggested that there is a total of about 38 million Thick-billed Murres in the northern seas.⁶¹³ Although these figures might be exaggerated, there are some very large colonies. More than 100,000 inhabit the Diomedes and the Cape Thompson area of Alaska. About 1.6 million breed on the Pribilofs while some 150,000 breed in the Aleutian Island area. The total estimate for all of Alaska is five million birds, although catalogued colonies in 1978 numbered under two million. Up to 215,000 Thick-billed Murres breed along the miles of cliffs among equal numbers of Thin-bills on Bear Island north of Norway.657 In Spitsbergen, where the total population consist of Thick-bills, there are rough estimates of up to two million birds.⁴³⁹ S.M. Uspenski estimated about two million, predominantly Thick-bills, at about 50 bird bazaars in Novaya Zemlya, and there are many birds in Siberian waters.⁶¹⁷ Large populations also occur on the western shores of Greenland and among the islands of northeastern Canada, where at least five million birds live in eleven colonies.⁴³⁴ More than 350,000 bred on Prince Leopold Island in 1958.⁴⁵ However, in 1975, censuses on the same island revealed only 172,000 breeding birds although numbers of nonbreeders were also present.^{210, 435} In a total of 18 Canadian Atlantic colonies in 1976, David Nettleship of the Canadian Wildlife Service estimated over 5 million Thick-billed Murres.⁴³⁴ In 1985, estimates indicated only about 3 million individuals for the same area, while total population for the entire Atlantic is presently about 15 million birds.⁴³⁹

Some studies have been made of the food consumption of Thick-billed Murres. The chick requires at least half its body weight in food each day. The two-week-old chick requires about 100 grams of food daily, and with this intake it triples its weight in about three weeks.⁶¹⁴ Uspenski calculated that the two million murres of Novaya Zemlya consume 25,000 metric tons of fish during the four months of the breeding season.⁶¹⁷ That his estimates are quite conservative is certain, since Tuck states that in the eastern Atlantic they consume twice that amount.⁶¹³

Study of stomach contents of 499 Thick-bills from the Barents Sea colonies revealed 77 percent fish remains and 23 percent mollusks, crustaceans, and mechanical admixtures such as grit and stones.⁶¹ The species of fish most frequently eaten by the Thick-bill includes Arctic cod, Atlantic cod, herring, capelin, sand lance, and sculpin. Tuck found that capelin constituted 93 percent of the stomach contents of 614 wintering Thick-billed Murres which he studied in Newfoundland.⁶¹³ At Gannet Islands, Labrador, 61 to 70 percent by weight, of the fish fed to chicks were daubed shanny (Lumpenus maculatus ) thus avoiding direct competition with the Common Murre which fed mostly capelin to their young.⁸⁷ To the north, at Prince Leopold Island, A.J. Gaston and D. Nettleship discovered that 90 percent of the summer food of Thick-bills is Arctic cod.210 In June, 1984,, at St. Matthew Island, Bering Sea, both species of murre along with other alcids were seen, by SCUBA divers, to be feeding on euphausiids below 30 m depth.²⁸⁸ Fish-eating alcids apparently will take any species available to them if the size is convenient for swallowing.²⁰⁴ In fact, murres of both species will swallow any slender fish up to 18 centimeters in length. However, there is reason to believe that a steady diet of one species of fish may not completely satisfy their dietary needs.

Slightly smaller in body length than the Common Murre, the Thick-bill stands about 48 centimeters tall and weighs an average of just under 1,000 grams. (Figure 5 in the Appendix illustrates annual weight changes in Thick-bills.) Its dorsal plumage is blacker than the Thin-bill's which tends to be brown, while the white of their breast forms a sharp point at the throat compared to a blunt taper on the throat of Thin-bills. In the breeding season Thick-bills can be identified by their distinctive white gape mark. In winter, the Thick-bill also lacks the black stripe trailing behind the eye which is distinctive for the commons in winter. Where the two species nest together on the same island, the Thick-bill prefers to be separate from the Thin-bills. Even though they may be found on the same ledge together, Thick-bills tend to be limited to the narrowest ledges rather than be too close to the dense masses of Thin-bills which shows dominance over Thick-bills, actually forcing them to the fringes and to the smaller ledges or submarginal areas.⁶¹⁷ This may lower their breeding success rate to 63 percent compared to 82 percent for the thin-bill.⁸⁷ Also associated with the Thick-bill is the kittiwake which nests on the available space left on cliffs, but the murre defends itself easily, and has the upper hand.⁶¹³

At Cape Thompson, Alaska, Thick-billed Murres arrive at their breeding cliffs before the commons which nests among the Thick-bills there.⁵⁹⁰ This is the opposite in the east coast colonies of Canada where Thin-bills arrive first.⁶¹³ One possible reason for the difference is that Cape Thompson is the northern limit for the Common Murre while the colonies in the Atlantic where the observations were made are approximately at the southern limit of the range of Thick-bills. Records on the Pribilof Islands to the south of Cape Thompson, also indicate that the Common Murre arrives first.

There is a present and absent cycle noted among the murres early in the prenesting period. Some days large numbers come to the brooding ledges, then most retreat to the sea again for a few days leaving the ledges almost empty of birds.⁵⁹⁰ Puffins, Dovekies, some auklets, shearwaters, and petrels also exhibit this same prenesting cyclic attendance at their nest sites. These patterns of attendance and absence are possibly related to the feeding needs of each species.

The Thick-bill is a demonstrative bird and, during the pre-egg-laying period, fights are frequent. Once a fight begins, it often continues for an hour or more and some birds have been seen to perish by having their bills twisted or torn off.⁶¹³ But once the nest sites are established, territorial behavior is not very pronounced and fighting is rare between recognized neighbors. However, any disturbance within or near the colony results in widespread bowing and growling. Copulation may occur as much as two months before egg laying and sperm production reaches its peak about two weeks before the egg is laid.⁵⁹⁰

Richard Perry, after studying Thick-bills at Spitsbergen, described six variations in the calls produced by adult birds, and these are remarkably similar to those of the Common Murre ranging from the running "murrrr-rr-rr" growls to yelps, wheezes and loud mirthless laughter.⁴⁸⁰ (See the Appendix Table 9 and Figure 23.)

Sunny days seem to encourage egg laying in high Arctic areas and the peak of egg laying lasts about ten days.⁵⁹⁰ On Canadian Arctic islands, the first eggs appear at the beginning of the third week of June.²¹⁰ Early eggs tend to be larger than those laid late in the season and give rise to heavier chicks.⁸⁴ Unlike the Common Murre which broods upright, the Thick-bill broods its single egg in the semiprone position.

Incubation lasts from thirty-two to thirty-four days, during which time the egg loses about 20 percent of its weight.²¹⁰ Sixty percent of the eggs hatch in thirty-four days and 80 percent of the birds which lose an egg replace it if the lost egg is no older than five days.²⁵⁰ Tuck discovered that eggs surviving for eight days have a 70 percent chance of hatching. Of 632 eggs in his study, 243 hatched, a success of 38.4 percent.⁶¹³ On Prince Leopold Island in 1975, David Nettleship recorded a hatching success of 84 percent resulting in total productivity of 80 percent.⁴³⁵ However, a particularly cold summer in 1978 caused almost 100 percent breeding failure.⁴³⁷ Breeding success may also vary from one location to another in the same year due to physical and environmental conditions presenting at the time of egg laying and chick rearing. Late ice thawing slows reproductive success.^{83, 84}

Parent birds occasionally assist a hatching chick by pecking away pieces of shell, and they feed it for the first time by the end of the third day. Estimated daily food intake by chicks three to eighteen days of age is 58 grams, almost 25 percent of which results in an equivalent weight gain in the chicks.²¹⁰

After five days, the chick is seen to shelter under its parents' wings. Body temperature begins to stabilize in about six to ten days but is not completely stable until the chick is ready to leave for the sea at eighteen to twenty-five days.³¹²

The chick is most prone to death in the first few days of life and of those that do perish, 38 percent die of exposure during storms, 41 percent fall from ledges, and 21 percent die from other causes. However, under ideal conditions, and in the absence of predation, almost 90 percent of the chicks fledge. On the average, about forty chicks go to sea for every one hundred pairs of adults. Upon fledging, the chick has usually attained about 12 percent of its adult weight.^{250, 590}

Cliff-nesting parents frequently demonstrate a slow "butterfly-like," fluttering flight, during which their wings are arched over their backs, nearly touching, as they encourage their flightless chick to take the plunge into the sea below.¹⁴⁴ The sea-going of the Thick-bill differs from that of the Common in the frequent competition by unsuccessful adults for possession of a chick. Very rarely, however, is the chick accompanied by both parents, as most often it is the male that convoys the chick.²⁵⁰ Nor do adults necessarily stay at sea with the fledgling since some adults return to the breeding location each day, for up to fourteen days, after the juvenile leaves.⁶¹³ First year birds apparently remain at sea and only a small percentage return to breed in their fourth year. Most do not breed until the fifth year.²⁰⁶

The Thick-bill does not winter further south than the 5° Celsius isotherm, which swings from Iceland down to Cape Cod and from southern Alaska to northern Japan in the Pacific. Rarely is it found far from the pack ice. Large numbers from high arctic breeding colonies, even some from Europe and Soviet islands winter where food is abundant on the west Greenland shelf and the Grand Banks east of Newfoundland.^{434, 462}

Man plays a role in exterminating this species. In Greenland alone it is estimated that man annually harvests 750,000 birds and 10,000 eggs. At least half a million are drowned annually when caught accidentally in fishing nets.⁵¹⁴ Studies of populations at Canadian Arctic Islands indicate a decrease in population of almost 50 percent since the mid 1950s. These declines are attributed to hunting and fishing pressures in west Greenland during the off-breeding season.²⁰⁴ Gulls prey upon eggs and chicks, especially when man trespasses on murre colonies. In fact, Glaucous Gulls physically attack murres to expose their eggs.²¹⁰ Snowy Owls, falcons, and hawks take their share, and when lemming are rare, foxes prey upon murres, storing eggs and carcasses in holes and crevices for winter use.⁶¹³ Fortunately, thousands of murres breed on high inaccessible ledges out of the reach of man and terrestrial predators.

Winter storms, and reduction in winter food supply,have been known to force birds from the Atlantic to the Great Lakes. The greatest of these wrecks, as the major destruction of birds by storms is called, occurred in 1894, displacing birds from the St. Lawrence region to southern Lake Michigan. Other peaks have occurred since then - the latest being in 1950.^205b Sudden freezing of Arctic waters in winter has also been known to trap many Thick-billed Murres.

Parasites also cause some deaths. Eleven species of endoparasites and five ectoparasites are listed for the murres. 384 A normal infestation, while undoubtedly shortening the life of the birds, probably does not affect the population level to a noticeable degree. A heavy infestation, however, may lead to emaciation and early death, particularly for a storm-weakened bird.

Calculations made by John Wiens and his colleagues indicated that after calamities, Thick-billed Murres are not a resilient species. An 80 percent mortality requires 80 years, or about 1 percent per year, for recovery.⁶⁵² At present, the figures indicate that its numbers are drastically declining. New international legislation and enforcement of existing protective laws are essential and urgent to save these murres from extinction. ^{183, 210, 436, 514}