Scientific name:Aethia pusilla
Aleut: Alama Gam Huligi; Choochkies
Japanese: Ko-umisuzume (Small Sea-sparrow)
Kuril Islands: Kurukura
Russian: Konyuga-kroshka (Tiny Auklet)

The Least Auklet though the smallest of the alcids, averaging 92 grams in body weight, is probably the most populous species in the Bering Sea. Descriptions by observers cruising the seas where the Least Auklet ranges are revealing of the population and characteristics: "immense flocks," "great swarms," "like a vast beehive," "curious birds with chunky little bodies surrounded the boat on all sides," are some of the impressions. It swarms in thousands about the rocky beaches of the Pribilof Islands, and on Diomede Islands in Bering Strait, one of the greatest breeding grounds, more than 250,000 Least Auklets breed.⁵⁷⁰

St. Lawrence Island is the home of almost 1 million Least Auklets. In eleven colonies there, the density has reached eighteen pairs for every 200 square meters. Between 1964 and 1969, a total of 953,000 birds used these colonies on St. Lawrence Island.⁵⁸ In 1978, the figures indicated a slight increase and in 1987 estimates were twice the original count. For all the known breeding sites in Alaska, there are possibly six million birds.⁵⁷⁰ We do not know how many breed along the Siberian coasts.

The Least Auklet nests from the north coasts of the Chukotski Peninsula to the Kuril islands, the Aleutian Islands eastward to the Semidi group, and the islands of the Bering Sea. The species wanders Southward in winter to the seas around Japan, and to the Washington coast ( more rarely to California) in the eastern Pacific.

According to some local observers, the Least Auklet often comes to land to shelter even in winter, but its real interest in the breeding territory begins, depending upon seasonal variations, about 1 May on the Aleutians and Pribilof Islands and about two weeks later around St. Lawrence Island. At this time it gathers in large flocks. In flight their swarms change shape, reeling and "twisting like drifting smoke: sometimes the bottom seems to drop out of the flock in sudden maneuvers".⁴⁰⁶ This swarming habit is considered to be a form of sexual display. They are first seen to land on their nesting slopes on St. Lawrence Island between 20 and 24 May where they speckle the snow fields above their nest positions.⁵⁸

Variation in the amount of white on the breast is seen in the Least Auklet. Breeding plumage includes considerable mottling of gray on the breast and flanks. The immature bird tends to be whiter below, and the throat of the adult is conspicuously white. A white streak spurs from the eye backward and downward, and white to yellowish plumes flare across the forehead. There is also individual variation in bill color, some having a brighter red to orange at the tip. The horn on the upper mandible also varies in height and as in one of a pair it is usually taller, it may have sexual significance.

Because of its small size the Least Auklet has a wider choice of nesting situations than the other auklets it breeds among. It nests among the rock debris which covers slopes, among beach boulders or in a sheltered covey along the top of a cliff or bluff where the rock pieces are relatively stable. It is considered to be a versatile nester, often found as isolated pairs on pinnacles and ridges of sheer cliff along with cormorants, puffins, and murres. Elsewhere the Least Auklets dominate areas where the average rock size is small.⁵⁸

Like the Crested and Parakeet Auklet the Least is most active during daylight, and the colonies are busiest during the early morning and evening. It feeds mostly on copepods, amphipods, decapods, and other invertebrates from the sea in the morning and early afternoon.

Least Auklets probably reach sexual maturity at three years of age, although younger birds may engage in breeding displays and activities. About 5 percent of the birds present on the breeding slopes are one-year-old birds, while up to 50 percent are two-year-olds.³¹⁶ Two-year-olds actively engage in social displays and courtship, and a small number apparently breed successfully, since they have been collected carrying food to nearly fledged chicks.54

Immature birds, by intruding on the displays of mature males, cause most of the constant and confusing squabbling at breeding colonies. It is difficult to tell which birds are mated pairs, but prolonged billing is indicative. Often three birds sitting peacefully together on a ledge will be suddenly dispersed by one of the three jabbing toward the other two until they take flight, whereupon the victor stands tall, chattering aggressively. The constant action reminds one of the nocturnal tussling and constant hustling seen among Cassin's Auklets. To avoid harassment copulation may take place in the nest. However, the bird frequently copulates at sea and at least attempts to on the rocks. The male bird engages in sexual display, which may be territorial in function, serving the purposes of defending the mate, the nest, and the display positions. Gradually, the commotion is reduced to duetting pairs on each perch, which eventually settle down to resting quietly side by side.

The Least Auklet vocalizes constantly on its display grounds, where the twittering, cackling, squealing, and peeping remind one of a cage full of budgerigars. Several variations are noted in its calls: (1) Warning or alert call. The bird stands tall and gives short "squeaky chirrs" or short repeated "cheeps", which vary in resonance from bird to bird. Some are quite shrill; (2) an aggressive "Chee-chee-chee" accompanied by nudging, pushing, edging, and lunge-pecking; and (3) duets between mated pairs. This is a constantly repeated "chee-chee-chee-chee-chee-chee" associated with billing and considerable head waving. Within the nest chamber, a more guttural, less piercing sound is made.

On the sea, pairs and larger groups sport about early in the breeding season. They chase and splash the water by vibrating their wings. rise up in the air, then plunge back into the sea again. They dive under, chasing one another to come up facing in all directions, then plough together again. Suddenly, in unison, the whole group takes to wing, circles the nesting grounds once or twice, then lands to squabble on the rocks.

Before egg-laying begins, Least Auklets visit their nest territories during the morning hours and by noon most have dispersed to the sea again. However, many return about an hour before sunset. In May on the Pribilof Islands, I have watched them congregate on the sea an hour before dusk. Within a few minutes, they began flying to land jostling one another until only a single pair occupied each perch. Crouched among the basaltic boulders, I stared towards the misted sea and watched them come until they were all around me. They knew I was there. Groups of them crowded together, stood tall on the highest boulders and driftwood, and peered and "chirred" in my direction. A few lost their balance when others flew in to join the commotion. Some flew so low that those perched were forced to duck their head. A few actually buzzed my head in similar fashion and as they passed they scolded with short squeals.

An hour later I noticed an almost synchronous change in nature of their chirps. The sounds became short and clipped, and then in silence, groups gradually began to leave, disappearing into the fog to spend the night in the chilling gray sea. As the season progresses, the Least Auklet spends more and more time on land until its egg is laid. Then more than half the population disappears into nesting nooks where both male and female often spend the night.⁵⁰⁷

Like the other auklets, this species lays only one egg . No evidence for re-laying has been observed and examination of the ovaries indicates that only one follicle matures.⁵⁸ No nesting material is gathered, the egg being deposited on the bare earth. The fresh egg is pure white with a smooth lusterless surface, and weighs about 17 grams or 20 percent of the adult body weight.⁵⁰⁷ Eggs appear as early as 28 May, although many are not laid until July. Both sexes incubate for twenty-nine to thirty-two days and both sexes develop double brood patches. Incubation patch temperature is 38° Celsius compared to an adult body temperature of 40.7° Celsius. Extra eggs added experimentally to the nests of this species are not accepted.530 Hatching success in studied areas may be as low as 49 percent.⁵⁴⁹ But in 1981 to 1982 on the Pribilofs, hatching success was 87 to 90 percent, 507 whereas on Buldir it was estimated at 68 percent.³³⁶

As in all bird populations, occasional albinism is seen. Spencer Sealy discovered an almost totally albino Least auklet chick on St. Lawrence Island. The 24-day-old bird was mostly white with buffy tan replacing the normally dark parts. Its eyes were pink, as were the legs and feet.⁵²⁸

Chicks are fed at all hours of the day from 0800 to 2230. However, there is often a lull in feeding frequency between 1500 and 2000. Their food consists of copepods, amphipods, and euphausiids transported in the parent bird's throat pouch.^{56, 504} When the chick is twenty-nine days old it ranges 81 to 91 grams or 88 to 108 percent of the adult weight and is ready to fledge.^{507, 530} A fledgling is not capable of sustained flight, and some die in the tide rips, to be eaten later by gulls. Overall breeding success may be 66 to 74 percent in some years.⁵⁰⁷ The young bird is not accompanied at sea by its parents, although the species is gregarious during the winter months accumulating on the sea in large flocks.⁵³⁰

The most important predators of the Least Auklet, next to man, are foxes and ground squirrels. The Red-backed Vole is also a possible cause of loss of eggs and chicks. The Herring Gull, when it has the chance, takes its share not only of the eggs and chicks, but also the adults. In order to gain access to eggs and young, Herring Gulls purposely cause massive panic flights among the auklets. Glaucous Gulls are apparently of less concern to the least Auklet on the Bering Sea Islands. Snowy Owls take a few and in the Aleutian colonies predation by falcons is severe, although the prevailing foggy conditions may serve as some protection.⁵⁴ Fortunately, because most nests are located in inaccessible places, Least Auklets survive well.

Although not as populous as the Dovekie of the Arctic Atlantic, the Least Auklet is a resilient and presently abundant species throughout its range. Consequently with adequate protection, there is no apparent danger to the survival of this species. Nevertheless, longterm studies will be important for more complete knowledge of the species.⁵⁴²