Pacific loon (Gavia pacifica)

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Pacific loon swimming
IUCN Red List species status – Least Concern LEAST
CONCERN

Top facts

  • The Pacific loon is thought to be the most abundant loon species in North America.
  • Fish and aquatic invertebrates form the bulk of the Pacific loon’s diet, and are typically swallowed whole while the bird is underwater.
  • The Pacific loon breeds in Alaska, Canada and far eastern Russia, wintering along the Pacific coasts of North America and Asia.
  • An awkward species on land, the Pacific loon can only take off from water, and requires an open stretch of 30 to 50 metres in order to do so.
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Pacific loon fact file

Pacific loon description

KingdomAnimalia
PhylumChordata
ClassAves
OrderGaviiformes
FamilyGaviidae
GenusGavia (1)

The Pacific loon (Gavia pacifica), also known as the Pacific diver, is thought to be the most abundant loon species in North America (2) (4). This large water bird (2) is a medium-sized member of the loon family (2) (5), with a long body (2) and a smoothly rounded head and neck (2) (4). The Pacific loon looks very similar to the Arctic loon (Gavia arctica), and was once considered to be the same species (2) (5).

In its summer plumage, the Pacific loon has a pale, silvery-grey head and hindneck (4) (5) (6) (7) (8), a dark forehead (8), and a black patch on the foreneck (4) (5) which is bordered by several vertical black-and-white stripes (4). The back is black with white checkering (5) (6) (7), while the breast and belly are white (4) (5). The Pacific loon has a straight, relatively thin, dagger-like bill, which is black and pointed (2) (3) (4) (7), and reddish (4) to deep red eyes (3).

During the winter, the plumage of the Pacific loon is drabber (5) (6), and is typically brownish-grey above and white below (4). However, the presence of a crisp, dark border down the side of the neck creates a sharp division between the white chin and foreneck and the dark grey hindneck (4) (6) (7). At the base of the neck, the dark colouration of the nape juts forward onto the white chest (8), and a dark ‘chinstrap’ may be present across the base of the throat in adult birds (4) (8). In non-breeding plumage, the bill of the Pacific loon tends to be greyer than in breeding birds (4).

Male and female Pacific loons are similar in appearance (4), although males tend to be slightly larger than females (4) (6). Juveniles of this species look much like non-breeding adults (2), with brown (4) to dark grey upperparts and a white throat, chest and belly (2). In addition, the feathers of the upperparts have pale edges (8).

The Pacific loon produces a repetitive, hoarse croak (2) or deep, barking ‘kwow’ call (7). This species is also known to utter a plaintive, high-pitched, yodel-like wailing sound (2) (5) (7) (9).

Size
Length: 58 - 74 cm (2)
Wingspan: 91 - 128 cm (2) (3)
Weight
1 - 2.5 kg (2) (4)
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Pacific loon biology

In the southern parts of its range, the Pacific loon begins to breed in March, whereas in the north the timing is dependent upon the arrival of spring (10). Following courtship displays, which may involve the birds swimming and diving in pairs, usually with ritualised head movements, loon species usually form monogamous breeding pairs. These pairs stay together for life and return to the same lake year after year, sometimes even using the same nesting site. Male loons produce a wide range of fascinating calls in order to advertise ownership of their territory and strengthen the pair-bond with their mate (12).

In all loon species, both the male and female take part in building the nest (12), which in the Pacific loon is typically a simple depression in the ground with minimal vegetation (2), or a heap or bowl of grasses and aquatic plants (2) (10) (12). Loon species tend to build their nests near the water’s edge (2) (10) (12), which enables them to escape easily to the safety of the water if threatened (12).

Pacific loon eggs are variable in colour, generally being buff, brown or olive-green (2), and usually one or two are laid per clutch (2) (12). Both the male and female take part in incubation (12), and the chicks leave the nest just one or two days after hatching (2). Pacific loon chicks are able to swim almost immediately, but may often be seen riding on the back of one of the adults for protection and to save energy. Young of this species take their first flight at about 50 to 55 days old (12).

The Pacific loon feeds mostly on fish (2) (5) (10) (12), but is also known to eat a variety of aquatic invertebrates (2) (10) including insects, molluscs, and crustaceans (10) (12). In addition, this species may supplement its diet with some plant matter (10) (12). Prey is caught underwater (5), with the Pacific loon diving after and pursuing its quarry before seizing the fish with its bill (2) (10) (12) and swallowing it whole, headfirst (12). On average, loon species dive for about 45 seconds at a time, but they are capable of remaining submerged for several minutes (12).

Pacific and Arctic loons are known to be more sociable than other loon species (12), and have been observed forming large groups and feeding cooperatively (2) (12). In addition, these species may migrate in flocks, which is unusual for a loon (5). Despite being agile underwater, the Pacific loon is extremely awkward in terrestrial environments, and is not capable of taking off from land. In order to take flight, this species requires an expanse of about 30 to 50 metres of open water, flapping its wings vigorously and pattering across the surface to gain lift (2).

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Pacific loon range

The Pacific loon breeds in Alaska and northern Canada (2) (3) (4) (5) (10) (11) as far east as Hudson Bay and Baffin Island (4) (5) (6) (11), and in far eastern Russia (3) (5) (10).

This species spends most of the year wintering along the Pacific coast of North America (3) (4) (6) (10) (11), from Alaska southwards as far as Baja California, Mexico (3) (4) (10), as well as along the Pacific coast of Asia (3) (10) down to eastern China (5) (10).

The Pacific loon has been reported as a vagrant in Greenland and Great Britain (5).

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Pacific loon habitat

During the breeding season in the summer months, the Pacific loon occurs on deep freshwater lakes within the tundra regions of its range (2) (5) (7) (10). In general, loon species tend to prefer large, undisturbed lakes that do not contain much submerged vegetation, as well as those which are dotted with small islands on which the birds can nest away from the threat of land predators (12).

The Pacific loon typically winters at sea along the inshore waters of the Pacific coast (2) (5) (10), although it can also be found in bays, estuaries (2) and occasionally inland (10). During migration, the Pacific loon rests on the open ocean (2).

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Pacific loon status

The Pacific loon is classified as Least Concern (LC) on the IUCN Red List (1).

IUCN Red List species status – Least Concern

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Pacific loon threats

There are currently no known specific threats affecting the Pacific loon. However, loons are shy species and are easily disturbed, meaning that several factors could potentially pose a threat to this species, including water pollution, entanglement in discarded fishing line, and fluctuating water levels on breeding lakes caused by dams (12).

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Pacific loon conservation

The Pacific loon has an extremely large range, and its population is thought to be increasing (10). As a result, there are currently no known conservation measures in place for this species.

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Find out more

Find out more about the Pacific loon:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Crustaceans
Diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
Incubation
The act of incubating eggs; that is, keeping them warm so that development is possible.
Invertebrates
Animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
Molluscs
A diverse group of invertebrates, mainly marine, that have one or all of the following: a horny, toothed ribbon in the mouth (the radula), a shell covering the upper surface of the body, and a mantle or mantle cavity with a type of gill. Includes snails, slugs, shellfish, octopuses and squid.
Monogamous
Having only one mate during a breeding season, or throughout the breeding life of a pair.
Nape
The back of the neck.
Territory
An area occupied and defended by an animal, a pair of animals or a group.
Tundra
Treeless, grassy plains characteristic of Arctic and sub-Arctic regions. They are very cold and have little rainfall.
Vagrant
An individual found outside the normal range of the species.
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References

  1. IUCN Red List (January, 2014)
    http://www.iucnredlist.org/
  2. All About Birds - Pacific loon (January, 2014)
    http://www.allaboutbirds.org/guide/pacific_loon/id
  3. Brazil, M. (2009) Birds of East Asia. A&C Black Publishers, London.
  4. Russell, R.W. (2002) Pacific loon (Gavia pacifica). In: Poole, A. (Ed.) The Birds of North America Online.Cornell Lab of Ornithology, Ithaca. Available at:
    http://bna.birds.cornell.edu/bna/species/657a/articles/introduction
  5. MobileReference (2009) The Illustrated Encyclopedia of European Birds: An Essential Guide to Birds of Europe. MobileReference, Boston.
  6. Kaufman, K. (2005) Kaufman Field Guide to Birds of North America. Houghton Mifflin Harcourt, Boston, Massachusetts.
  7. Peterson, R.T. and Peterson, V.M. (Eds.) (2002) Field Guide to the Birds of Eastern and Central North America. Houghton Mifflin Harcourt, Boston, Massachusetts.
  8. Kaufman, K. (2011) Kaufman Field Guide to Advanced Birding: Understanding What You See and Hear. Houghton Mifflin Harcourt, Boston, Massachusetts.
  9. Arlott, N. (2009) Birds of the Palearctic. HarperCollins UK, London.
  10. BirdLife International - Pacific loon (January, 2014)
    http://www.birdlife.org/datazone/speciesfactsheet.php?id=3867
  11. Dennis, R. (1993) Loons. Voyageur Press, Minneapolis.
  12. Mobley, J.A. (Ed.) (2008) Birds of the World. Marshall Cavendish, Singapore.
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Pacific loon swimming  
Pacific loon swimming

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