Scientific name: Brachyramphus marmoratus
Alternate name: Partridge Auk
Japanese: Madara-umisuzume
Russian: Pestriyi Pyzhik

Geographically, Marbled Murrelets form two separate populations, one on each side of the northern Pacific. One race breeds along the Siberian Coast of the Sea of Okhotsk, while the eastern race breeds from Kodiak Island, Alaska, south to Northern California. The western race is slightly larger than the North American subspecies, with notably larger wings. A few pairs are found along the Aleutian Islands and stragglers have been reported near islands in the Bering Sea during the summer months. ¹¹⁶ In winter the species ranges south to San Diego.²³⁰ Many records indicate that Marbled Murrelets use coastal freshwater lakes in British Columbia and Pacific Northwest States not only in the breeding season, but also during winter. ^{129, 546} Rare specimens in healthy condition have been collected in lakes as far east as Indiana. ⁴⁰²

For almost two hundred years years Marbled Murrelets kept their nesting place a secret. Observers near the beginning of the last century reported hearing these birds heading inland at night and returning down the valleys toward the sea. In those days Indians believed that they nested in hollow trees high in the coastal mountains. ¹²⁶ However, though diligently sought by many ornithologists, no nests were found, although an egg found in a mossy situation 15 miles inland in Washington State, by E.J. Booth in 1927 has now been authenticated as a Marbled Murrelet's egg.³³⁵

Kuzyakin, a Russian observer, described the first documented nest of the Marbled Murrelet on 17 June 1961.347 This nest was located on the branch of a larch tree about 7 kilometers from the sea, and 12 kilometers northwest of Okhotsk, Siberia. The tree was 12 meters tall and the nest was about 7 meters above the ground and 25 centimeters from the tree trunk. A single egg nestled in a cushion of moss 14 by 17 centimeters in diameter and 1 to 4 centimeters in height. Previously, eggs were positively known only from specimens taken from the oviducts of mature birds at sea.⁵⁵⁵

A few years later, in 1967, during lumbering operations, about 6 kilometers from the sea on Vancouver Island, British Columbia, two young murrelets fell with a cedar tree, adding further evidence that the species nests in trees.²⁵⁷ Undoubtedly, the birds have been felled with trees many times by lumbermen who failed to recognize or see them.

A third discovery was made by Hoyt Foster in 1974 while he was trimming dead limbs from a Douglas fir tree.⁶⁷ The tree towered over a campground 10 kilometers from the sea in the Santa Cruz mountains of northern California. This was an excellent find, for the nest contained a downy young, the first to be seen directly associated with its nest. It does seem strange that a seabird would nest in trees far away from the sea.

An especially fortunate find by Theodore Simons on 8 July 1978 on East Amatuli, Barren Islands, Alaska modified the developing tree-nesting picture.⁵⁵⁴ Simons chanced upon a Marbled Murrelet incubating an egg on the ground and followed the stages of nesting for fifty-one days. The data from this nest are among the most exciting information about murrelets this century, and provides information which enables us to reevaluate previous theories about the species. Since Simon's find, several other nests on the ground have been described including one in a shallow cavity. ³¹⁴

The single 41 gram egg found by Simons was in a small depression on the ground and was "pale olive-green covered with irregular brownish black, tar-colored spots." Previous descriptions indicate that the color varies considerably. The nest site was at an elevation of 68 meters and only about 75 meters from the shore in a shaded position at the base of a rock outcrop.

Through daily observation Simons discovered that both sexes incubate in twenty-four hour shifts but that the egg was left unattended during a very stormy day. The egg hatched on 1 August, twenty-five days after discovery, into an alert 34.5 gram chick which grew rapidly. It was alone in the nest the day after it hatched and within nine days the feathers had begun to show beneath the down. However, the camouflaging down was retained as a cover until just before fledging on Day 27. On the last day, Simons saw the chick preening away and actually eating its own down.⁵⁵⁴

During the 1979 season on 7 July, Kathie Hirsch, Doug Woodby and Lee Astheimer found a nest no more than 10 meters from Simon's 1978 nest.²⁷⁴ This nest also contained an egg, which hatched on 20 July. The nestling period was confirmed at 28 days. The chicks in the two nests monitored fledged at an average weight of 145 grams, or 65 percent of the adult weight.⁵⁵⁴ (see Figure 12 in the Appendix.)

It seems reasonable that the Marbled Murrelet would choose to nest in a position on the ground or in a tree which offers the best camouflage for its egg and young, and which provides a suitable background to hide the incubating adult. Protective coloration is little protection, however, from predators which sniff out their prey. But predators likely to find the eggs, young, or adults in trees would most likely be those which depend more upon sight than smell.

Hawks, owls, crows, ravens, martens, and squirrels may be the only predators with which the Marbled Murrelet must contend while nesting in trees. Those that nest on the ground may also suffer predation by foxes and rats. Peregrine Falcons and Ravens occasionally may take a few and at sea large fish may possibly devour them. Simons noted that both adults and chick sit low and motionless on the nest, although remaining alert when predatory species fly over.⁵⁵⁴ But, once again human activity is the greatest hazard to their numbers. Almost eight percent of their total population is killed each year in gillnets during salmon fishing season in British Columbia. Unfortunately fishing season coincides with the bird's breeding time.¹²⁸ It is apparent that Marbled Murrelets raise only one chick each year. Spencer Sealy studied the ovaries of Marbled Murrelets and indicated that normally only one egg fully matures each season.⁵³⁴

On the sea Marbled Murrelets are frequently seen in pairs. During the summer at Deception Pass State Park in Washington, pairs may be observed during daylight, merely floating for hours with the current. One of a pair is always on the alert, with the head lifted high while the other bird floats low in the water with the head and neck withdrawn. Pairs often engaged in diving just below the surface as if chasing prey, but prey was seldom brought to the surface. Between dives, they actively bill-dip and wing-stretch standing up high out of the water. Perhaps the shallow dives, instead of for feeding, were episodes of courtship behavior, or mutual sporting equivalent to the water chases seen in guillemots (Cepphus ).

The Marbled Murrelet takes flight easily from the surface of the water without skittering far, prefering to dive rather than to fly at the approach of a boat. In late June through July birds have been observed off Rosario Head, Washington, during the hour before sunset, actively feeding or holding fish in their bills. In water 12 meters deep, dives between 15 and 155 seconds in duration were recorded with as little as five seconds between dives. However, they may drift on the surface for 45 minutes or more without diving. The average time of 13 dives recorded was 45 seconds.⁶⁰³

During courtship displays, both birds of a pair extend their bills upward, uttering shrill calls. Frequent high-pitched whistles and loud piercing cries keep paired birds in contact. They vigorously paddle around together following a random path for several minutes and dive repeatedly.⁶⁰³

The incubation period of the Marbled Murrelet has been calculated at about thirty days. The first adults seen carrying fish at dusk, before flying in to feed their young were recorded on 13 June 1979 in the Queen Charlotte Islands area. In the same locality, Spencer Sealy reported that the first young appeared on the sea accompanied by two adults on 7 July 1970. Although sometimes with adults, the young bird is more often seen alone or in twos.⁵³⁴

According to observations and extrapolations of the movements of Marbled Murrelets, the best time to look for nests, at least along the Canadian west coast, is from 15 June to 8 July. This is the period when most pairs are incubating their egg, and the young which have hatched in earlier nests have not yet left for the sea.534 The Alaskan nests are a few weeks later.554

Some authors have suggested that the young Marbled Murrelet walks to the sea by following small streams. Such a journey would be difficult and highly hazardous for a young flightless bird and even adults do not walk well on land. 386 But they are not flightless when they fledge. Those who have most closely studied their habits agree that the fledgling Marbled Murrelet flies to the sea under the cover of darkness. Is it possible that parent birds guide the chick to the sea, or does it leave on its own, guided by instinct? Some observers have seen large groups of excited adult Marbled Murrelets on the sea just before the young are ready to join them in the water. Others have found no correlation between the grouping of adults and the time at which the young are ready to leave the nest. Their behavior patterns remain a challenge to ornithologists.

The Marbled Murrelet adult averages 25 centimeters in body length and the average weight, combining seventy-four adult males and females is 223 grams. Range in weight varies between 188 and 269 grams.536 As demonstrated in other species, the mean body weight varies slightly with the time of the year, the bird being heaviest during the month of May.

Immature birds return to Canadian coastal areas, along with breeding adults, in late April. At this time young birds comprise about 15 percent of the population.536 An immature bird can be distinguished from an adult by the condition and histology of its reproductive organs; the absence of brood patches; and the active molting in late April. Adults have by that date completed the spring molt. Marbled Murrelets undergo a complete annual molt after the breeding season in September to November.339 At this time they may become temporarily confined to the water.643 (See the Appendix for graphic molting sequences Figure 20.)

Sixty-four percent of the food items taken near Langara Island in July consists of sandlance (Ammodytes hexapterus). Other fish making up the rest of the diet, are capelin, Pacific herring, and especially during the winter, euphausiid and mysid crustaceans.635 When feeding the young, the adult has been seen to carry up to four fish and it is suggested that parent birds probably make only one trip each night with fish for their young.534 With such limited feeding, it is amazing that the chick grows as rapidly as it does. A chick reared far inland may eventually be found to have a slower growth rate probably because of less frequent feedings.

In 1988, David Marshall compiled the known information about the Marbled Murrelet emphasizing the need to preserve areas of mossy mature forests in which the species breeds along the Pacific coast of North America.³⁸⁶ Such action may also help preserve other species such as the Northern Spotted Owl. Clear-cutting should obviously be avoided in areas of concern and at the same time alternate remunerative plans must be made for the benefit of lumbermen who consequently lose their income.

By using telemetry (attaching small radios to birds), other tree nests have been located - two in Southeastern Alaska and one on Kodiak Island. Two more tree nests were found and observed in a Californian Douglas Fir forest in 1989. In 1990 and 1991 twelve Marbled Murrelet nests were located in trees of coastal range forests in Oregon and Washington and four more were reported in southcentral Alaska.⁴²⁴ Also in 1991 in Big Basin State Park in California a nest was located in the crotch of a Coast Redwood tree that lacked mosses and lichens. Now the search is on for others and an interest- group formed to seek preservation of mature forest habitat along America's western coast, and to study the species habits more intensively. As of 1995 more than two dozen nests have been located on the limbs of moss-laden trees in the coastal ranges. It may be found that where there are no trees, as demonstrated by ground nests in Alaska, Marbled Murrelets could be successful nesting on the ground in the coastal ranges provided that predator pressure is not increased.

Because of the current thrust in the interest of Marbled Murrelet habits new insights should soon be available. In the meantime it appears that clear-cutting of mature forests along the western North American Coast may be a major threat to their breeding success.