Scientific name: Ptychoramphus aleuticus
Aleut: Makcheethah
Spanish: Alcuela Norte americana

The Farallones, located about 43 kilometers west of the Golden Gate, support one of the largest seabird colonies along North America's western coast. Here, the Cassin's Auklet, the alcid with the wrinkled nose, as it genus name implies, haunts the night with activity and the sounds of its burrowing and breeding. Estimates in recent years suggest that about 52,500 pairs are found here. This number includes a large number of floaters - birds capable of breeding but lacking space - and many nonbreeding birds which are perhaps too young to breed. ³⁷⁸

The Cassin's Auklet is a species preferring the more temperate parts of the coast from Alaska south to 27° north latitude. Early in this century, the Cassin's Auklet was a common bird on all islands as far south as Asunciķn and was reported there as the most abundant seabird. ³²⁰ Recent population studies on the most southerly islands indicate that the species is rare, if not completely absent, because of the presence of feral cats. However, about 10,000 to15,000 pairs still breed on Channel Island.

Small populations exist on suitable islands along the northern Californian, Oregon, and Washington coasts. Beyond the northern end of Vancouver Island is Triangle Island, where the largest known colony of at least 360,000 pairs breed. ^{633, 635} Approximately 65,000 pairs breed on Frederick Island, and about 10,000 pairs breed on Ramsay Island of the Queen Charlottes; a few are also found on other islets of British Columbia. ^{587, 633}

Recent exploration catalogues over 300,000 birds in Alaskan waters in 21 known breeding sites. ⁵⁷⁰ It appears, then, that the total population of Cassin's Auklet may be more than 1,600,000 individuals. It is well to be cautious though. Because of the bird's nocturnal habits at its breeding grounds, it is possible that some estimates may be far too high. Occupancy is usually much lower than the total number of burrow entrances, thus counts made on the basis of the number of burrows are not liable to be accurate.

Occasionally, the species is recorded on inland waters. Two records are known of the birds on the Willamette River near Portland, Oregon, and a stray specimen has been recorded in the Kuril Islands to the north of Japan. ^{303, 344}

The male and female are identical in external appearance. The newly molted adult has a dark, dusky gray mantle with a gray throat and a white belly and lower tail coverts. (Figure 18 in the Appendix illustrates the timing of molts in the Cassin's Auklet.) As the plumage wears, the edges of the feathers become frayed, and lose their pigment. The bird then has a mottled tan appearance and, during the months of August and September, birds may be seen with badly worn wing and tail feathers. In this condition, some may not be able to fly. Others continue to incubate and raise young while molting. ⁴⁷³ In the adult, the pupil of the eye is black, set in a white iris. A juvenile bird has dark brown irises and a bird breeding for the first time may have brown flecks in a white iris. The white eyes, then, are a sign of sexual maturity. Adult birds vary between 152 to 200 grams in weight and average about 23 centimeters in body length. ^{376, 600}

Cassin's Auklets may be found visiting their breeding grounds, at least in the southern end of their range, every month of the year. A few late nesters extend into late November. When the meager rainfall comes to the Farallones toward the end of December, the auklets return in large numbers to begin preparing their burrows for a new nesting season. It is then that the dampened soil, otherwise soft and easily eroded, facilitates burrowing. However, heavy rain seems to inhibit their activity at this time. Although they seem to prefer to dig burrows of varying length, they may be found using every well-covered nook and cranny of suitable size. They nest under boulders and driftwood, and on some islands under mats of grasses and between the roots of trees. In northern California, on Castle Rock, they burrow deeply into the sod under tufts of rank grass as they do on the Shumagins in Alaska. The burrows on these deep soils are variously branched, with blind alleys or frequent curves and spirals.

On the Farallones, the birds also tunnel under the foundation of buildings inhabiting every dark corner. They nest in the recesses of caves and dig into the accumulations of guano deposited by the Brandt's Cormorants. Nests can be found anywhere from a few meters from the spray zone to the highest parts of the islands, about 100 meters in elevation.

Those who have ventured into auklet territory at night are aware that these peculiar birds, although visually evasive because of their nocturnal habits, are far from being aurally secretive. The auklet chorus has been aptly described as the sound of a frog pond in full cry or of squealing pigs. The sound not only resembles a frog pond in full cry but there is also a tendency for the sounds to begin simultaneously. Often the entire colony is silent for fifteen minutes or more, then in the distance one individual will begin with a few notes as if to tune in the others. Within seconds the whole island is again acroak with their "kreeking." When producing the sound, every muscle seems to be called into use: the throat puffs out and the whole body squeezes the vibrant sound through the vocal apparatus.

At least ten variations of the vocal theme are readily identified. Upon arriving from the sea about an hour after sundown, the auklet plops clumsily to the ground within a meter or two of its burrow entrance. It scampers along the ground, half hopping, half running, often uttering a short, clipped "krick" as it submerges into its hole. When the incubating mate is present, a series of gutteral "Ker-chuck-Ker-chuck" sounds are emitted by the incubating bird as a greeting.

One evening I sat in a cave near a groove along the edge of the cave's floor where a twenty-day old chick waited for the return of it's parents to feed it. I waited in silence, partly reclining on a piece of cardboard, with my camera set to take flash pictures of the feeding process. My patience was rewarded. At about the usual forty-five minutes after sundown, a flutter of wings and a thud near the cave entrance indicated that an adult was entering. There was silence for a moment; then I heard a distinct clicking sound apparently produced by the snapping of the bill. This was an immediate signal to the young at the nest site, which began its begging -- a constant "cheep-cheep." The adult navigated in the total darkness toward the sounds of its chick. It treated my body as nothing more than another rock in its way as it paused on my legs for a few moments, then fluttered down to creep between my body and arm. The nearer the adult came to its nest the louder the chick chirred, and I could tell when contact was made by the chick's excitement. The chick vigorously and excitedly nibbled at the parent's bill and head upon contact.

The adult responded with a few quiet twitters, standing erect then bowing forward to force food from the special throat pouch under its tongue. Sipping sounds indicated that feeding was in progress, so I reached for the camera shutter. The resulting blinding flash disturbed the feeding process for only a few seconds, then it continued again in response to the chick's impatient begging.

Sounds made by the adult bird during mating, greeting, and social activities are variations of a basic cricket-like chirring or "kreek-kreek-kreek-kreek." The "kreek" sound varies in duration, pitch, and frequency. During a full-cry chorus of hundreds of birds, sudden changes in rhythm occur. A repetitious "krick-i-er" may switch to a "kreeka, kreeka," or to "kut-reeah." A "kreer-kut" sound is frequently reversed to "kut-reeah-kut-reeah" and in this variation it reminds one of the sounds of the shorebird, the Killdeer (Charadrius vociferus).

When on the ground or circling about in the air, pairs are heard to utter mutual trilled and warbled "kreerr-er,kreerr-er" sounds between considerable twitterings. Aggression initiates a growled "krrr,krr,kr," and the warning call is a loud "kreer." (See sonograms, Figures 24-26 in the Appendix.)

From late December until mid-March on the Farallones, the Cassin's Auklet burrows, cleans, repairs and mates. New burrows begun during the night of 18 January were one meter in length by 17 March. A pair seeking a new nesting place explores every nook and cranny, even entering buildings to examine every corner of every room. They scratch the substrate here and there, each of a pair "kreeking" and bowing to the other and running here and there in short spurts until a suitable burrow site is located. Excavation takes place with no less ceremony, both birds sharing in the digging. On one occasion, a pair was seen alternately scratching out the beginning of a new burrow. They started on flat ground by kicking soil from a central point in all directions. Both feet bearing needle-sharp claws dig alternately, scattering soil often for a meter or two. After a depression is made on the ground, the birds concentrate on one side, enlarging it into a cavity. Progress is not rapid because of the many pauses to run, hop, bow, kreek, and to threaten neighbors. Usually only 5 to 7 centimeters are dug in one night. As the season progresses, more time each night is spent in such activities.

Plucking weeds and pecking at the bare ground are also seen. A few pieces of plucked weeds are taken into the burrow and strewn the entire length. Occasionally a mat of plant material is formed at the end of the burrow on which to lay the egg but most often the single egg is deposited on the bare soil.

Mutual displays include recognition and greeting movements characterized variously by back-stepping, circling each other, sudden about-facing, head-bobbing, and bowing. The arriving mate is often greeted with side stepping part way around the mate, billing, nebbing and repeating "chirr-chirr-chirr" sounds. Head-bobbing may be equivalent to head-flicking as seen in the Atlantic Puffin. The waggling head from side to side, raising one wing toward a partner, and "passing" each other are also frequent actions by a pair of birds. "Passing" is displayed when one bird of a pair, after sitting for a period, hops or runs ahead of its mate. Its mate follows and passes the first bird, pausing just ahead. Passing is often continued with each bird alternating the procedure for several meters ending with one of the pair quickly about-facing to bill, or with both birds flying a small circle to return to the original starting point near the burrow entrance. These actions may precede coition which has been seen, on one occasion, to occur upon a rock. It is possible that coition occurs most frequently at sea as it does with other auklets or perhaps it may occur within the burrow.

Forward-jabbing is an aggressive pecking thrust toward an intruder. A rock used as a perch is defended in this way. Face-to-face combat in rooster style is the ultimate in aggressive action and is not uncommon. In this, the opponents face each other with tails erect, wings partly raised, and head feathers ruffled. Their heads waggle and contact is made by leaping at each other with their sharp claws raised. Fights often end with the arrival of a third bird.

Chases involving up to a dozen birds all switching roles from one moment to the next are similar to the water sporting of the Pigeon Guillemots. These chases which are mildly aggressive in nature may be interpreted as social displays. Sporting displays include forward-jabbing, pecking, feather-pulling, and "leapfrogging." Leapfrogging in the Cassin's Auklet occurs when a pursued bird suddenly stops and turns quickly to face its opponent which, having gained momentum in the chase, jumps over the one that faces it. Two birds may leap each other three times in succession, each turning upon the other to give chase or to tag. "Leap-frogging" is used to describe a different activity in guillemots. However, the aerial chases of the Pigeon Guillemot show a similar character when the pursued bird attempts to escape by making sudden 90° or 180° turns in the air.

During the early stages of breeding activities, before incubation and rearing the young, weather conditions influence the time and numbers of birds going to their islands. Clear, windy conditions seem less favorable than overcast and foggy nights. Later in the season movement to and from the islands is more predictable. ³⁷⁸

In the early season before egg-laying is at its peak, and just before dawn, pairs of birds demonstrate departure ceremonies. In March for example, pairs of birds begin leaving the island about one hour before sunrise; about 70 percent leave in pairs, the rest singly. Those which depart alone are perhaps unmated birds or birds leaving mates incubating eggs.

The "departure ceremony" was seen only between pairs and may be considered a mutual display. The display begins when one of a pair utters a loud "kree-er" call. The mate responds by moving to the caller's side, and then both advance together toward a take-off point. One takes the lead. Often the pair sits at the take-off point for five minutes or more, then without apparent signal the birds rise off their tarsi in unison, back step, bounce two or three times, bow, and fly off side-by-side toward the sea. They utter squeering calls as they go, as if pursued to sea by the grayness of dawn. The ceremony is readily recognized by the back step, bounce, and bow. A single bird merely "squeers" as it flies off.

Some authors have suggested that the Cassin's Auklet is nocturnal to avoid predators while others suggest that its feeding habits are responsible. However, studies of other auklet species bring some doubt to either suggestion and the real reason for the nocturnal preference may yet to be discovered.

In 1932, van Rossem, while exploring San Benitos Island, off Baja California, found Cassin's Auklets incubating eggs on 2 February. This is the earliest known date for fresh eggs for this species. ⁶²¹ On the Farallones, fresh eggs are usually abundant by the Middle of March. Egg development depends somewhat upon environmental conditions such as ocean temperature and food availability. ²⁰ Cassin's Auklets lay a single egg which is creamy-white when fresh, the creamy reflection being given by the dark orange yolk. As incubation proceeds, the eggs develop a greenish hue owing to the reflection of the dark down of the chick through the white shell. Stains from nest substrate also blotch the eggs.

Some observers have been unable to determine whether or not a distinct brood patch is developed and note that the Cassin's Auklet warms its egg under various parts of the body, even under the wing. ^{474, 599} Another observer describes two lateral incubation patches which refeather midway through the incubation period and which lack the obvious network of blood vessels seen in other species possessing well-defined brood patches. ³⁷⁷ It seems that the brood patch in Cassin's Auklet is not well-developed and may not function throughout the vital latter stages of incubation.

Relative to egg mass (28g) Cassinšs Auklets have the longest incubation period of all alcids.²¹ It ranges from thirty-seven to forty-two days, with an average of 38 days. ^{376, 600} Lapses in incubation sometimes occurs in auklets, as it does among various species of petrels, and tends to lower the metabolism of the developing chick as well as prolonging the duration of incubation.²¹ Both parents share equally in the incubation duties, usually exchanging roles daily.

Hatching of the egg usually occurs after two or three days of pipping. Incubation continues until the chick is about four days old, at which stage the chick is able to maintain its body temperature and therefore remain alone in the burrow. The chick hatches with a full coat of soft down which is dark gray dorsally and light gray ventrally. Its eyes are blackish-brown with an area immediately around the eyes tending to be free of down. Frail legs and pink feet and toes are tipped with black claws. At hatching, weight of the chick ranges from 13.0 to 20.0 grams, averaging 17.8 grams or 10.6 percent of the average adult weight. Although some chicks remain in the nest for fifty days, most have left the burrows for the sea within forty-five days of hatching. The average nestling period on the Farallones for sixteen birds was 41.1 days with a range of thirty-five to forty-six days. In a 1971 study, chicks gained 3.9 grams per day until an age of thirty-seven days when the nestlings lost 2.3 grams per day until fledging. ³⁷⁵ (See Figure 13 in the Appendix for graphic comparison of growth in auklet chicks.)

The ten-day-old chick is still quite small, soft and downy but the legs have changed from pink to gray-black with a light blue cast to the upper toes and tarsus. At fifteen days, feathers begin to appear. These are first evident on the belly, dorsal midline, and wings. By the eighteenth day feathers begin to appear on the neck and head. Wing primaries begin to plume by twenty-three days and by then the belly coverts are conspicuously white under the thinning down. Patches of down often adhere to the nape and rump until the chick is forty days of age. The fledgling begins exercising its wings when thirty to thirty-five days of age. Soon after dusk the young bird is seen near the burrow entrance, stretching and flapping its wings for extended periods. Between periods of exercise it returns to the confines of its burrow. When forty days of age, the juvenile begins jumping into the air and running along the ground in attempts to become airborne. The first flights are short, up to 10 to 15 meters, and usually end in clumsy crashes. Eventually it becomes aware of its "landing gear", but some crash to their death before ever reaching the sea.

As has been mentioned, food is transported by a parent bird in a baglike extension of the mouth cavity called the gular pouch, which opens under the tongue. A young bird without breeding experience lacks such a pouch and in a bird breeding for the first time, the pouch begins to lengthen only after egg-laying. It reaches a maximum length of 130 millimeters in the adult at about the time the chick leaves the nest. After feeding of nestlings is over, the pouch shrinks to about half its size until the next breeding cycle. By comparing birds with or without gular pouches, Steven Speich and David Manuwal determined that 27 percent of the total population of the Cassin's Auklet on the Farallones were young birds without breeding experience. ⁵⁷²

The chief food brought to the young is a small, pink euphausiid shrimp, Thysanoessa spinifera. This is the only euphausiid near the Farallones abundant during the daytime near the surface of the sea. This small shrimp is found mostly in the upper one hundred meters of sea with a high density in the upper four meters. ⁴⁷³ Others have found the same euphausiid to be the main food item during the breeding season at the northern limits of the Cassin's Auklet range. Another species, Euphausia pacifica, is also used for food and swarms of copepods, Neocalanus cristatus, enable high reproductive success on British Columbian islands. ^{629, 634} A single Cassin's Auklet may carry almost 25 grams of food to its chick each night. ⁵⁷² Kees Vermeer found that early breeders have greater success and higher weights than late breeders on Triangle Island, British Columbia due to the early abundance of copepods. ⁶²⁹

It is also interesting to note that food during the breeding season is sufficiently abundant enabling the parent bird to feed its chick and at the same time begin its postnuptial molt. Primaries are lost a few at a time, allowing most birds to continue to fly. ⁴⁷³

Occupied parts of burrows are kept free from fecal material. The young bird usually deposits its liquid wastes toward the entrance of the burrow, marking it with conspicuous pink coatings.

Total mortality of eggs and young may be as high as 73 percent. The highest loss, 33 percent, occurs in the egg stage when the desertion rate is high. Some eggs are lost when shallow burrows cave in. Of the eggs which hatch, 8 percent of the chicks die in the hatching process and of the chicks which hatch successfully the mortality may be 35 percent. The annual combined mortality rate of one, two and three-year-old birds is estimated to range between 45 and 55 percent. This high mortality rate is apparently a periodic phenonemon caused by fluctuations in oceanic currents, such as El Nino,which changes water temperatures and thus food supply for breeding marine birds.⁵²³ One to three-year-olds normally comprise about 30 percent of the total population on the Farallones where they do not breed until they are at least three years of age. Here, because of the lack of space, many do not have the opportunity to breed until they are four or five years old. ⁵⁷²

On the Farallon Islands, gulls seem to be the worst enemy. Where the auklets burrow in gull territory, many are found dead with pecked skulls. In other areas, gulls may be seen foraging for chicks among the shallow burrows. Young auklets have been seen being carried off by gulls to be torn to shreds, or if small, swallowed whole. David Manuwal also noted considerable damage done to burrows by cormorants which moved through the Cassin's Auklet territory on the Farallon Islands, rooting up vegetation for nesting material. ³⁸⁰

Storms too, take their toll on this bird, as witnessed by the numbers found dead on beaches after severe storms. If oil spills were to occur between seven kilometers southwest and sixteen kilometers northwest of the Farallones, or near Triangle Island, British Columbia, a large portion of the known Cassin's Auklet population could perish, since its main feeding grounds are located in these two places.

Cassin's Auklets do not spend extended periods at sea. The early breeders, which most likely are the more experienced birds, would have the most time to stay at sea. The breeding season or time spent on land is extended for this species, and the birds can be found at night at any month of the year on the Farallones. Their presence or absence is staggered according to the age and experience of the birds. Younger birds which may be sexually capable of breeding, and which even may be mated, may have to wait until space is available after the older birds have reared their young and left. David Manuwal identified a large population of floaters among the Cassin's Auklet population. ³⁷⁸ He found that most floaters were young birds, although some were older ones which had perhaps failed in their first attempt at nesting for the season. These usually try again if it is not too late in the year. It would seem then, that the breeding and survival rates of this bird could be increased if artificial, gull- proof, non- collapsible, burrows were provided, as is currently being done on the Farallones in conjunction with recent research.^{20, 21}

In areas of the Farallones, where it nests in rocky situations, the Cassin's Auklet may share available spaces with the Ashy and the Leach's Storm Petrels. However, there is little competition. The smaller storm petrel nests in spaces between rocks, in rock walls, and under objects much too small for the auklets. These petrel species also use the islands every month of the year, although in fewer numbers during winter months.