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Species Database

Gavia pacifica - Pacific Loon

Pacific Loon image

Geographic range:

Arctic to Baja California

Key features:

A medium sized loon that winters on the Pacific, usually well off shore. In summer, both the Pacific and Common Loon have a bold black and white checkered pattern on their back, but the Pacific Loon has an ash-colored head and neck, whereas the Common Loon has an almost iridescent green-black head and neck.

Similar species:

Gavia immer -- Common loon
Gavia stellata -- Red throated loon

Habitat(s):

bay (rocky shore), bay (sandy shore), estuary, exposed rocky shore, exposed sandy beaches, kelp forest, protected rocky shore, protected sandy beaches
 

Primary common name:

Pacific Loon

General grouping:

Seabirds and shorebirds

ITIS code:

174475
 

Geographic Range

Range Description:

It breeds in tundra regions from Alaska east to Hudson Bay and south to northern British Columbia, Manitoba, and Ontario; and as far east as Baffin Island, and in Russia east of the Lena River. It winters at sea mainly along the Pacific coast and on large lakes over a much wider range, including China, Japan, North Korea, South Korea, USA and Mexico. It has occurred as a vagrant to Greenland, Hong Kong and Great Britain.

Habitats

bay (rocky shore), bay (sandy shore), estuary, exposed rocky shore, exposed sandy beaches, kelp forest, protected rocky shore, protected sandy beaches

Habitat notes:

In central California, they can be seen nearshore or well offshore, and in estuaries and lagoons while transiting from the Arctic to Mexico.

Abundance

Relative abundance:

Uncommon. In the MBNMS area it is a fairly common winter visitor, concentrating in large flocks beyond the kelp line over deep water several miles off shore. They are rare in the summer. During spring migration they pass the Monterey Bay area during March through May, with their numbers peaking in April. The Pacific Loon is the most abundant of the five loon species that breed in Alaska with an estimated statewide total of 100,000-125,000 in 1992. Its population in Alaska appears stable. It is a common winter visitor to deeper Pacific coast waters, and migrates by the thousands in the spring and fall along the outer coast. Because they are scattered over deep water several miles from shore they are difficult to study.

Species Description

General description:

The Pacific Loon was considered a subspecies of the Arctic Loon, but is now classified as a full species. They are very similar. Like the Arctic Loon the Pacific Loon is a medium sized loon. There are 5 species of loons, the Red-throated Loon is the smallest, the Pacific and Arctic Loons are medium sized, and the Common and Yellow-billed Loons are the largest. It has a blackish brown and white checkered back and white underparts in breeding plumage. Its forehead, crown, lores, and ear-coverts are a dark gray, paling on the upper nape and down the back of the neck to pale gray. Chin, throat, and foreneck are black with the lower throat and foreneck glossed with purple. The throat is crossed by a narrow transverse band of short vertical white streaks and the sides of the neck and upper breast have a series of long longitudinal narrow white and black streaks. The tail is blackish brown with white underparts except for a dark line across the vent. Sides are glossy black. It has a smoothly rounded head and neck. Its’ body is long and rides low on the water. The white of the belly is exposed when the loon rolls to preen or when it is riding high on the water, but otherwise only a narrow line of white is exposed. Its eye is red and is adapted for both aerial and underwater vision. Its bill is black in breeding season and gray in the winter, slender, dagger-like, and approximately 2 inches long. It is held horizontally when sitting on the water. Non-breeding plumage is a duller black-brown, duller black on the back, and dark brown on the sides. Chin, throat, and breast is all white with a dark necklace at the top of the throat. The back of the head is gray, much darker than in breeding plumage. The feet are set far back on the body, trailing behind when in flight, with neck outstretched in a direct flight with rapid wing beats. On ground it has great difficulty walking due to the placement of the legs so far to the rear. It cannot take flight from land and requires 30 to 50 meters of open water to flap and patter across the surface of the water to achieve flight. Like all loons the Pacific Loon is a fish eater, catching its prey underwater. Adults have an annual molt while on the wintering grounds. Both sexes have similar plumage. In all plumages the lack of a white flank patch distinguishes the Pacific Loon from the otherwise very similar Arctic Loon. On their breeding grounds they have a variety of sounds. They are noisiest at sunset and sunrise with most vocalizing occurring at nesting ponds. They also call in flight during the breeding season, even while carrying a fish in their bill. Their common call is a guttural kwow or kwuk, often repeated in a yodel-like high-pitched wail. It can be heard at great distances. These yodels are given only by the males and are thought to be a territorial statement. Other calls given on the breeding grounds are a grunt or croak, similar to a raven’s croak, and quiet wails and yodels often given as a duet by a pair. Their wail is described as a plaintive cry: ah-hah-wee, with the last syllable high and penetrating. Individuals sometimes wail back and forth to one another in a cadence, with many joining in to form a great mournful chorus, which has been described as ‘a wild satanic serenade.’ Little is known about their vocalizations during the non-breeding season.

Distinctive features:

The Pacific Loon is approximately 20 inches long and is a diving bird with a long body that rides low on the water, holding its black bill horizontal to the water. Its back is black with white checkering and the head and neck are ashen in summer dark grey the rest of the year. Chest, throat, and belly are white, with dark stripes at top of the throat. It is awkward on land and requires 30 to 50 meters to flap across the water to gain flight.

Size:

Size: Medium-sized loon; male is slightly larger than female Length: 58-74 cm (22.8-29.1 in) Wingspan: 110-128 cm (43.3-50.4 in) Weight: 1-2.5 kg (35.3-88.2 oz)

Natural History

General natural history:

The Pacific Loon is the most gregarious of all the loons. While migrating or when food is abundant they may be seen in flocks of several thousand, although most observations in the Monterey Bay area are of a single loon or a pair. It spends most of its time on the Pacific except for three summer months on arctic and subarctic tundra lakes and rivers for breeding. During periods in spring and fall in the Monterey Bay area they are abundant as they migrate along the Pacific Coast. The rest of the year they are harder to find, preferring arctic breeding ponds and Mexican wintering waters.

Predator(s):

Predation on adult Pacific Loons has not been observed, however eggs and chicks have many predators including Long-tailed (Stercorarius longicaudus) and Parasitic jaegers (S. parasiticus), foxes (red fox [Vulpes vulpes] and/or arctic fox), and possibly Glaucous Gulls (Larus hyperboreus). Evidence suggests that jaegers are primarily responsible for destruction of island nests, while foxes destroy shore nests. Herring Gulls (Larus argentatus), Thayer’s Gulls (Larus thayeri), and Sandhill Cranes (Grus Canadensis) also take loon eggs. Other species that alerted adults caring for young were Mew Gulls (Larus canus), Arctic Terns (Sterna paradisaea), Sabine’s Gulls (Xema sabini), and Common Ravens (Corvus corax) suggesting that these species are perceived as possible predators of chicks.

Prey:

Fish, especially stickle backs and sand lance, and aquatic invertebrates are main sources of nutrition for the Pacific Loon. Their diet varies from season to season. When at sea (9 months of the year) they eat mainly fish. In other habitats they will also consume fairy shrimp, tadpole shrimp, ologochaeties, gastropods, insects, such as water boatmen, caddisfly larvae, dragonfly nymphs, water fleas, stonefly larvae, chironomid larvae, and other aquatic life. On Monterey Bay market squid (Loligo opalescens) and pelagic fish such as medusafish (Icichthys lockingtoni), and northern anchovy are parts of their diet. They may also consume shiner perch (Cymatogaster aggregata), minute surfperches, Pacific herring, and juvenile salmon.

Feeding behavior

Carnivore

Feeding behavior notes:

Pacific Loons feed while on the water. They repeatedly dip their heads in the water looking for prey before diving. They are excellent swimmers and divers, propelling themselves generally using their feet alone and seizing their prey with their bill. Pacific Loons stretch their necks up and erect to full length before going underwater, usually jumping upward slightly before diving. In contrast, Common Loons simply slither under slowly as they dive forward. When foraging from the surface, the Pacific Loon may stir up the bottom sediments with its bill. During breeding season when feeding their young, they most often forage in waters that are close to their nest, but will feed themselves elsewhere, taking foods both at sea and in freshwater wetlands. Pacific Loons on Monterey Bay may occur in large mixed-species groups of Brandt’s Cormorants (Phalacrocorax penicillatus), gulls, Brown Pelicans (Pelecanus occidentalis), Common Murres (Uria aalge), Western Grebes (Aechmophorus occidentalis), and Rhinocerous Auklets (Cerorhinca monocerata). They also occur in single species groups. Foraging Pacific Loons sometimes attract commensals, such as gulls, that wait for the loons to bring fish to the surface and then snatch it.

March - June

Migration:

The Pacific Loon is a medium-distance migrant that leaves its breeding range in late winter, shifting from freshwater inland sites in the Arctic to coastal marine habitats along the Pacific Coast. The North American population winters mostly in Mexico. Little information exists on when they depart from Mexican wintering waters. They are highly gregarious during migration with aggregations of thousands seen resting and feeding in shallow passes between the Channel Islands in the Southern California Bight and in groups as large as 1,000 on Monterey Bay. Resting flocks of several thousand have been observed along the Oregon coast in May and June. Along the California coast migration is observed in late March, peaking in mid- to late April, with movement northward possibly continuing into June. Loons migrating from the Gulf of Mexico probably travel overland to the Pacific Coast. This first stage of their spring route remains a mystery. From San Diego northward, some migration occurs along the immediate coast, but many take a route well offshore across the southern California Bight, thus large spring migrations are seldom evident along the coast. From Point Conception to Oregon migration is along the coast or slightly offshore. Coastal migration along Washington and British Columbia is also the norm. It is unknown whether they take a short-cut across the Gulf of Alaska. Evidence suggests that their migration is diurnal, with the migration in force by sunrise. They travel in conspecific flocks, sometimes with a few Common and Red-throated Loons mixed in. They pass within a narrow band stretching from shore-line out several hundred meters to several kilometers offshore. They fly at altitudes <100 m, usually <10 m and often just over the water’s surface. Along the Arctic Coast of Alaska, where coastal waters may remain frozen when the migrants arrive, they tend to travel along open leads in the ice. The flocks may number from 10 to an almost continuous string lasting all day, especially if prey items are readily available. As they reach the northern edge of their range it is believed that they break into pairs and that individuals are usually mated by the time they arrive at their nesting sites. Some non-breeding loons over-summer within their winter range.

June - August

Reproduction:

Upon arriving at their Alaska breeding areas in the arctic and sub-arctic tundra on the shore of the mainland or on an island, migrants will gather in small flocks and begin looking for open water. As soon as there is a thaw a monogamous pair will occupy a space, but will defer nest building until water levels begin to drop and semi-dry nest sites become available and as soon as sufficient melt water is available for take off and landing. Many of the loons are paired in the spring in the Arctic while still on salt water as they wait for the ice to thaw inland. Others have already paired off by the time they arrive. They move to nesting ponds as soon as the melt is adequate, usually within a week after their arrival on the breeding grounds. Low, flat areas adjacent to water are preferred, allowing them to take flight from the water. Nests may be a rudimentary depression with small amounts of vegetation pulled from nearby water. This type of nest is easily and quickly built and eggs can be laid within a few hours after construction begins. Or if the pair selects a site that is under several centimeters of water a more built-up nest requiring complex behaviors must be constructed of bottom mud and up to two bushels of aquatic vegetation. It has a well molded basin and a firm rim. Materials used include Sphagnum moss, sedge, grass stalks, roots, mud, and decaying vegetation. This type of nest, as high as 46 cm and as wide as 76 cm, takes time and energy, which delays the start of laying eggs by a day or two. Nests may actually be completed after the first egg is laid. Parents defend their multipurpose territory vigorously with displays and calls. Each pair has territories for resting, preening, displaying, copulating, nesting, brooding, and feeding young. The boundaries are distinct and along the shore. Surrounding land is not defended. These territories are used repeatedly from year to year. Pre-reproductive behaviors of the pair include bill dipping and splash diving followed by underwater rushing. Then the females have a ritualized behavior prior to copulation. When the pair is near the shore the female climbs up on the shore facing inland, raises her tail exposing white under feathers and presses her bill against her breast. The male then mounts her. Then within minutes they return to the water and preen. No copulations have been observed on the water. Usually two seven cm long, brownish, slightly speckled with dark brown, eggs are laid two days apart and are incubated for 23 to 25 days, hatching asynchronously. The chicks are semi-precocial, active and covered with down, and able to leave the nest in two days. The chicks are cared for by the female until they are about 18 days old. Then the male also participates in parental duties. When the young are 1 to 2 days old they are led from the nest by the female to different locations on shore and to nearby wetlands to find prey items. Parents also forage for their young away from the nest pond, flying as far as necessary to fish and return with a fish carried crosswise in their bill. However it appears that young are primarily fed invertebrates and small pond fish. Parents feed the first hatched chick, while the second chick receives food only after the first chick is satisfied. Thus there is a high mortality of the second chick. The family stays together until late summer or early autumn. The young begin flying from the nest pond, circling the area and landing again in the nesting pond at 50-55 days of age. They fledge, leaving the nest pond when they are 57-64 days old, and fall migration commences.

August - December

Migration:

Migration may start as early as August for Pacific Loons breeding in eastern Alaska and northern Canada. Those breeding in western Alaska and Canada depart usually in September. Individuals remain in sheltered bays or the open ocean from September through early November. Unlike other loons, the Pacific Loon may migrate in huge flocks. Timing of fall migration in the Pacific Northwest varies greatly from year to year. Southbound migrants, perhaps non-breeders or failed breeders, begin to pass Washington in August, peaking in October. Oregon has its peak in late October and early November. First arrivals in California are seen in September. In Monterey their migration spans mid- October to mid-December, peaking in November. As many as 120,000 Pacific Loons have been observed massed on the north end of Monterey Bay in November, 1997, undoubtedly because of abundant prey items. Some travel well offshore, primarily over the continental shelf, 5-110 km offshore.

November - April

Feeding:

The Pacific Loon winters at sea, mainly on the Pacific coast, or on large lakes over a wide range, including China, Japan, North and South Korea, USA, and Mexico. It is believed that they move between wintering sites as food availability changes. They seem to prefer coastal salt water, chiefly nearshore open ocean, but also large bays and estuaries. Along the central California coast large feeding flocks develop beyond the kelp line and out to deeper water more than 15 km offshore. In Monterey Bay they are found most often over sandy bottom substrate rather than over rocky bottom. Off the Pacific coast of Baja they are found most often in lagoon channels close to mouths of bays.

Listing Status:

The IUCN lists the Pacific Loon as of Least Concern. It has a huge range, estimated to be between 100,000 to 1,000,000 square km. The global population is estimated to be between 930,000 to 1,600,000. However they are vulnerable to pollution in offshore wintering areas, to destruction of habitat in the northern breeding grounds, to oil spills, to incidental mortality in gill nets, to disruption from humans, and disturbance from airplanes flying over.
Click on an image below to view a larger version in the SIMoN Photo Library. You will also be able to view important information on each photo such as photographer, date, caption and more.
Ehrlich, P., D.S. Dobkin, and D. Wheye. 1988. The Birders Handbook: A Field Guide to the Natural History of North American Birds. Simon & Schuster Inc., New York. 785 p.
NOAA. 1994. Beached marine birds and mammals of the North American West Coast: a revised guide to their identification. NOAA Sanctuaries and Reserves Division, U.S. Department of Commerce
Roberson, D. 2002. Monterey Birds 2nd edition. Monterey Peninsula Audubon Society, Carmel, CA. 536 p.
Sibley, D.A. 2000. The Sibley Guide to Bird. Alfred A. Knopf, Inc. 545 p.
Truett, J.C. and S.R. Johnson. 2000. The natural history of an Arctic oil field: development and biota. Academic Press. 422 p.
WWW
Alaska SeaLife Center
http://www.alaskasealife.org
Accessed 10/30/2010 for Surf Scoter

WWW
BirdWeb
http://birdweb.org/birdweb/
Accessed 08/30/2010 for Ruddy Turnstone
Accessed 10/10/2010 for Pacific Loon
Accessed 12/04/2010 for Bufflehead
Accessed 02/20/2011 for Western Sandpiper

WWW
Cornell Lab of Ornithology
All About Birds
http://www.allaboutbirds.org/guide/search
Accessed 05/17/2009 for Albatross
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Accessed 04/13/2009 for Heermann’s Gull
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Accessed 01/26/2010 for Pigeon Guillemot
Accessed 12/15/2009 for Black-crowned Night Heron
Accessed 07/07/2009 for Pied-billed Grebe
Accessed 04/04/2010 for Osprey
Accessed 08/30/2010 for Ruddy Turnstone
Accessed 10/10/2010 for Pacific Loon
Accessed 10/15/2010 for Sooty Shearwater
Accessed 10/30/2010 for Surf Scoter
Accessed 12/04/2010 for Bufflehead
Accessed 02/01/2011 for American Coot
Accessed 02/20/2011 for Western Sandpiper
Accessed 03/04/2011 for Least Sandpiper.
Accessed for California Condor

WWW
WhatBird.com. Field Guide to Birds of North America.
http://www.whatbird.com
Accessed 12/30/2008 for Black-footed Albatross
Accessed 01/30/2009 for Pelagic Cormorant
Accessed 02/28/2009 for Marbled Godwit
Accessed 04/14/2009 for Willet
Accessed 04/13/2009 for Heermann’s Gull
Accessed 09/10/2009 for Eared Grebe
Accessed 06/20/2010 for Black Turnstone
Accessed 12/15/2009 for Black-crowned Night Heron
Accessed 10/13/2009 for Horned Grebe
Accessed 10/10/2010 for Pacific Loon
Accessed 10/30/2010 for Surf Scoter
Accessed 02/01/2011 for American Coot
Accessed 02/20/2011 for Western Sandpiper
Accessed 03/04/2011 for Least Sandpiper.