Scientific name: Cepphus carbo
Alternate names: Spectacled Guillemot; Ring-eyed Scoot
Aleut: Kayurka
Japanese: Keimafuri
Russian: Ochkovyi; Chistik

The chief external differences between the Sooty Guillemot and other closely related guillemots are its 10 to 20 percent larger size, the lack of the white speculum on the wings, and the presence of white markings around the eyes which inspires its alternate names. It is worth noting that the subspecies of Pigeon Guillemot nearest in geographical range to the Sooty Guillemot, on the central Kuriles, also has minimal white in the wings. The Japanese name, Keimafuri, means "the bird with the red legs" a feature shared with the other two species of Cepphus. The vernacular name Sooty Guillemot is used here because it matches appropriately the species name "carbo".

Both sexes are alike in color, and in the summer the whole plumage is sooty-black, fading through gray to white around the eyes. As in the Black and Pigeon Guillemot, the winter plumage is a mottled gray and white. The color of the mouth however, is a lighter hue being more of a flesh-pink color than the intense vermilion seen in the Pigeon Guillemot. In the breeding season, red legs and white face patches are conspicuous markings especially when the bird is in flight. The white facial feature also camouflages them well when they rest on dark rocks where the white matches the spatters of fecal material.

The Sooty Guillemot ranges along the coast and islands of the Sea of Okhotsk and the Sea of Japan. The best known breeding area in Japan is Teuri Island located off the northwest coast of Hokkaido where about 7,000 once were reported to breed.²² However, population counts made during two months of observation during the 1981 breeding season revealed only about 400 birds at the Teuri Island colony.⁶⁰² Colonies twice the size inhabit Soviet islands to the north.⁴¹⁷ Although the species is considered frequent along the coasts of the Sea of Okhotsk, the species only sparsely populates the remainder of its limited breeding range where it scatters along suitable coastline in single pairs or in small groups of about five or six pairs. No close estimate of total breeding population has been made, but the total number in the range probably does not exceed 30,000 birds.

The Sooty Guillemot is a sensitive bird-more easily disturbed at its breeding locations than its congeners. Although individual variations are obvious most members of the colony on Teuri Island in 1981 were cautious and skittish near their nesting locations. The sight of human intruders in the area tended to keep them away from their nests, except at the peak of the island where tourists frequent an observation platform. Here they were quite accustomed to human disturbance. When carrying fish to feed their young they were invariably harassed by Black-tailed Gulls (Larus crassirostris) which attempted to snatched the fish away from them. Because of this kleptoparasitism by the gulls, the guillemots usually made direct flight into their nest chamber when delivering fish to their chick.⁶⁰² Displays and mating activities of the Spectacled Guillemot begin in early April and are very similar to those of the other guillemots. However, their display postures are in some respects less intense. For example, in aerial chases they are never seen to actually make bodily contact in the air as do the Pigeon Guillemots.

The sounds produced by the Sooty Guillemot are weaker than those of the Pigeon Guillemot. For example, the strong "seeeooo" of the alarm or warning scream of the Pigeon Guillemot is reduced to a thinner sounding "seeee" in the Sooty Guillemot. The "tsit" or "chip" sound is similar in all three species of Cepphus and is given at varying intervals, even in flight.

The trilled call lacks the "seeeooo" addition in the middle of the call usually heard in Pigeon Guillemots and in this respect more closely resembles the descriptions given for the Black Guillemot. Sten Asbirk refers to this call in the Black Guillemot as the "nest song," which rightly identifies it with nest territory ownership.¹³

Squat-peeping is one of the most common social displays seen in all three species of guillemots. Some observers have interpreted it as an aggressive display.^{13, 165, 420, 497} However, Sooty Guillemots do not always reveal an aggressive action. Squat-peeping is sometimes demonstrated by a single bird in a group or at the nest site when an intruder lands nearby and is normally associated with strut-circling by a second bird. Strut-circling is characterized by frequent head-dipping while swimming around the squat-peeper, or waddling when on land. Squat-peeping may be a sign of being mated. When a mated bird, sitting near its nest entrance or on the water below the nest site is approached by an intruder the former begins to Squat-peep. This attracts the mate if it is within calling distance. When the mate arrives it responds by circling the squat-peeping bird. This demonstration usually encourages the intruder to leave without being attacked. Otherwise the arriving mated bird displaces the intruder by strutting, hunching or attack.

Twitter-waggle is an aggressive display common to all three species of the genus although it has been interpreted in the Pigeon Guillemot to be an appeasement action.¹⁶⁵ In the Sooty Guillemot, the action is strongly aggressive and frequently performed by individuals among groups on the water or on land. Birds jostling for the highest position on the rocks display twitter-waggle constantly. It is also a major part of aquatic displays and is always a mechanism for increasing distance between birds. Once a single Sooty Guillemot was seen persistently twitter-waggling toward a group of communally bathing Black-tailed Gulls. This bird was obviously attempting to drive the gulls away, although the gulls appeared to ignore it. Other features of behavior are identified and tentatively interpreted in Table 11 of the Appendices.

One or two eggs, similar in color to those of the other two species of guillemots, are deposited in rock cavities from about two to 100 meters above the sea. On Teuri Island in 1981 if two eggs were laid, often only one hatched. If both eggs hatched the second chick died within three days. No nests were discovered in the 1981 breeding season on Teuri Island that successfully reared two chicks. The reason for this was not clear. Mr. Matutoshi Aothuka, a warden for the care of birds on Teuri Island who has been banding birds on Teuri for many years, stated that he has never seen a guillemot rear more than one chick. This is strange because the other two species often rear two chicks and may be capable of rearing three. It may be, that food availability is a limiting factor in northern Japan and also to the north, where it is reported that only one chick is reared.⁴¹⁷

The two eggs of a single clutch are not always marked alike, a feature also noted in the Pigeon Guillemot.⁶⁰⁴ However, the two eggs from the same clutch of Danish Black Guillemots always have the same ground color and a similar pattern of spots.¹³ Ten eggs on Teuri averaged 60.4 x 41.70 mm with a range of 57.60 to 63.80 x40.3 to 43.8 mm. These were smaller than 14 eggs measured by Nazarov and Labzyuk who on more northerly islands found a range of 61.1 to 66.8 x 41.1 to 45.2 mm. Nine eggs at late stages of incubation ranged in weight from 50.0 to 60.1 g. ⁴¹⁷

Both sexes share in the incubation which lasts approximately thirty to thirty-five days. ¹⁵⁴ On Teuri the chicks begin hatching at the beginning of June which means that mating activity begins early in April in northern Japan. The warm water of the Sea of Japan apparently contributes to the early onset of breeding there, compared to similar latitudes of the North American coast where Pigeon Guillemots begin their activity at least a month later.

The chicks of Sooty Guillemots, upon hatching, look just like the young chicks of the other two species. They have a full covering of sooty-black down. The legs and feet are pink, turning black in a day or two. The bill is also black with a prominent white egg-tooth on the top mandible, while at the tip of the lower mandible a smaller egg tooth is also present. These teeth gradually wear off, but in the three chicks observed to fledging, a remnant of the upper one remained up to the 40th day. Chicks hatch with a body weight of less than 40.0 g, reach a peak of 605 g by Day 38, and decline to 545 g the day before fledging.⁶⁰² Adult body weight varies from 415 to 545 grams.¹⁵⁴ The chick is fed approximately five times per day until it is 40 to 45 days old.

Body and wing feathers begin to show on days 12 and 15 after which the belly feathers develop a mixture of white and sooty black. The head, neck and dorsum, including the wings and tail, are a uniform sooty-black by fledging time. The eyelids are white and an area around the eyes, destined in maturity to become white, remain naked until close to fledging when it fills in thinly with fine grey feathers. The feet and legs upon fledging are black or dark grey.

About 12 days after leaving the nest the fledgling's plumage changes from slaty to a mottled brown, while the feet and legs become red by Day 20. The young birds are independent from the time they leave the nest and may even be driven away from groups of mature birds.⁶⁰²

Adults begin to molt early in July even while still feeding young. As in other species of auks they probably become flightless for a short period, when the wing and tail feathers are lost, until complete winter plumage is developed. They are fairly sedentary birds and do not wander far from breeding areas during the winter months.