Cepphus grylle
black guillemot

The Black guillemot is a circumpolar species distributed in boreal, low arctic and high arctic regions of the North Atlantic and Arctic oceans. Black guillemots can be found in coastal areas from the Gulf of Maine, New England across parts of the northern coast of North America, as far as Alaska. In Europe and Asia they are found from the British Isles and northward across the northern coast of Asia. The largest concentrations can be found among islands of the high and low arctic. Wintering populations disperse as far south as Rhode Island in North America and France in the eastern Atlantic (Johnsgard 1987; Nettleship and Evans 1985; Nettleship 1996).

Generally Black guillemots are restricted to rocky shores due to their nesting requirements. They nest most often in crevices among stones and boulders at the base of cliffs or cracks in cliffs, and less often under rocks among vegetation and under driftwood. In the high arctic some cliff sites may be as high as 230m. Artificial cover (debris on shore, harbor walls, under buildings) has allowed guillemots to nest in areas where they may not have previously.

Foraging habitat varies dramatically with the seasons. During the breeding season birds forage in inshore waters generally less than 50m in depth. Although they remain fairly close to shore year round, in winter months black guillemots are more pelagic, frequently feeding along pack ice edges where pack ice occurs. Some overwinter in polynyas of the high north (Brown 1985; Cairns 1992; Harris and Birkhead 1985; Johnsgard 1987; Nettleship 1996; Winn 1950).

A relatively small seabird, Black guillemots are approximately 32cm in length. In breeding plumage, as their name implies, Black guillemots are black from bill to tail. They also have large white wing patches, and bright red feet, legs and inside the mouth. As many as seven sub-species have been described based on variations in size, bill and wing length, and plumage. After an early fall moult adults take on a patchy black and white plumage that has been described as "salt and pepper" and legs become a paler red. This winter plumage retains the white wing patch on the black wing, however the body plumage becomes white below and barred black and white above with a black bill and mostly white head. Newly fledged birds are similar to wintering adults and yearlings have an adult-like plumage with brownish spots in the white wing patch (Bedard 1985; Gaston 1985; Johnsgard 1987; Nettleship 1996; Stokes and Stokes 1996).

Black guillemots form monogamous pairs and show remarkable site fidelity, returning to the same colonies and often the same nest site year after year. Their social behavior ranges anywhere from solitary pairs to highly colonial. In the southern portion of their range guillemots are less social and less colonial, living in colonies of 10's and 100's while birds of the high arctic occur in colonies as large as several thousand. In some areas nesting habitat will overlap with other Alcids (Razorbills, Alca torda and Atlantic puffins, Fratercula arctica) with one documented case of Razorbill and guillemot eggs in the same hole.

Black guillemots show a variety of social behaviors towards each other. They are territorial over nest sites, perching sites on stones and strongly defend perching sites above nests. Aggressive behaviors include the typical guillemot call (high-pitched, open mouth whistle), lunging attacks with open bills, aggressive walk stance (hunched posture and wings partially opened), and surface, aerial and underwater chases. "Leap frogging" chases have been described with individuals flying over others and landing in front of the other on the water. Around Grand Manan Island, Canada, groups of up to 40 or 50 individuals have been observed swimming in lines possibly as a group foraging technique since members of the line often continuously look underwater by dunking their heads followed by simultaneous dives (pers. obs.) Fairly elaborate courtship displays have been described involving head bowing, whistling, pairs turning and swimming in circles, and males stepping up and down with alternating feet while standing on females backs during copulation (Cairns 1980; Harris and Birkhead 1985; Johnsgard 1987; Nettleship 1996; Winn 1950).

Like other members of the Alcidae family, C. grylle are adapted to wing-propelled swimming allowing them to dive deeply where they feed mainly on fish on or near the seafloor. Prey items include sandlance (Ammodytidae), gunnels (Pholidae), sculpins (Cottidae), pricklebacks (Stichaeidae), Arctic cod (Boreogadus saida) and many other fish as well as many invertebrates: polychaetes, molluscs, jellyfish, crustaceans, sponges, crabs, and even barnacles. They are known to dive for nearly 2 minutes and up to estimated depths of 50m. Many patterns of foraging behavior have been found. There is typically a morning, and sometimes evening, peak in foraging activity, but in some areas feeding may be continuous throughout daylight hours. Foraging distribution has been shown to change with tidal cycles where birds prefer waters of moderate flow. Seasonal cycles also exist with guillemots feeding inshore during the breeding season and farther offshore or around pack ice edges during the winter (Bradstreet and Brown 1985; Cairns 1986; Cairns 1992; Johnsgard 1987; Nettleship 1996; Nol and Gaskin 1987; Winn 1950).

During the 1800's and first half of the 20th century Black guillemots were taken for food; adults were hunted, young collected and eggs taken from nests. These activities were known to occur in parts of eastern Canada (mainly Labrador and the Gulf of St. Lawrence), Iceland, Faeroe Islands, British Isles, areas of the White Sea, and many Scandinavian countries. Many laws prevent such activities now (Nettleship and Evans 1985).

Black guillemots have no threatened status and are quite abundant, especially in some regions of the high arctic. Total population of the North Atlantic and Arctic oceans was estimated in 1985 at 270,000 pairs (200,000-350,000). In some areas population declines have been observed. In the past local reductions may have resulted from hunting or egging. Currently some populations seem to be increasing and expanding their distributions. Locally introduced predators, oil spills, and commercial gill-net fishing may impact guillemots, however there are no serious threats globally. High rates of nest visits by scientists have also been shown to decrease nesting success (Brown and Nettleship 1984; Cairns 1980; Johnsgard 1987; Nettleship and Evans 1985; Nettleship 1996).

As was mentioned above, Black guillemots forage inshore during the breeding season and generally lay 2 eggs. This is typical of other guillemots (Pigeon guillemot, Cepphus columba and Spectacled guillemot, Cepphus carbo) but atypical of most members of the Alcidae family who forage far from shore and produce a single egg. Explanations for this distinctive strategy suggest that the inshore foraging and the double clutch go hand in hand. With Alcids it has been suggested that clutch size is a function of food availability or the ability of adults to provide food for young. Therefore guillemots have developed an inshore foraging strategy during the breeding season giving them easy access to food during chick rearing periods. This may allow them to raise more young than long-distance foraging Alcids. Studies of Black guillemot energy expenditure during chick rearing support this hypothesis (Birkhead and Harris 1985; Mehlum et al. 1993).