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Gavia pacificaPacific loon(Also: Pacific loon;diver)

By Peter Herbst

Geographic Range

The Pacific Loon is found along the Western Coast of the United States during the fall and winter, and in Northern Canada and Alaska where they migrate for the breeding months of the spring and summer.

Habitat

Pacific Loons reside for the most part along the eastern coast of the Pacific Ocean and Arctic Ocean along Canada's northern boundary. They can also be found in inland waterways and even lakes occurring along their migratory paths. They are sensitive to disturbances, especially those created by humans, and are most likely to occur in remote areas. Their nest are found right along the shoreline and will be abandoned if receding waters cause the nest to be too far from the edge of the water. Recently loons have become a pest on lakes that are commercially stocked with fish.

  • Aquatic Biomes
  • lakes and ponds
  • coastal

Physical Description

The Pacific Loon's head is black which extends down the back of its neck and back where there are some mottled white spots. On its underside the color is white extending from its bill to its belly. Its average length is 66 cm.

Reproduction

Pacific Loons are monogamous as long as the relationship is producing offspring. Breeding takes place in the spring and summer and is relatively noncompetitive once a mate is found for the males defend territories and mate with the same female each year. Loons are extremely awkward on land and venture out of the water only to nest. Broods usually include a total of two eggs, one of which is laid a few weeks before the second. This first egg also is the first to hatch, and it is brooded while the other egg is incubated. The older offspring assumes the dominant position in the nest and will be the first to be feed throughout its development. During times of inadequate food resources parents commonly continue feeding their older offspring, leading to the death of its younger sibling.

Behavior

When loons have young, they will often transport them on their backs to decrease chances of predation and to keep the young chick warm. The young are completely dependent on their parents for the first 5-7 weeks but by the eighth week it will have developed fishing abilities to go off on their own. When finding mates, fighting will occur between the males in the population. Males use their beaks to spear their competitors and they often mortally wound each other.

Communication and Perception

Food Habits

The Pacific Loon feeds mainly on small fish and other aquatic life. Fishing is conducted beneath the surface where they make good use of well-developed air sacs, which allow them to pursue their prey for extended periods.

Economic Importance for Humans: Positive

Loons are aesthetically pleasing to observe in the nature and they are well known for their distinctive calls, which commonly occur at night.

Economic Importance for Humans: Negative

Loons may be considered pests by commercial fishermen, who see them as competitors

Conservation Status

Pacific Loons are found in low concentrations during the winter months and in higher densities during the breeding months. This loon is combating human pressures well, but populations may decrease in the future. Recent studies are looking into the magnification of chemicals in the loon's body due to pollutants being added to the ecosystem and the loon being near the top of its food chain. The Pacific Loon's range is growing smaller as human development encroaches on its preferred habitats.

Other Comments

The Pacific Loon, until recently, was considered to be the same species as the Arctic Loon, but the two are now distinguished as separate species.

Contributors

Peter Herbst (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

visual

uses sight to communicate

References

Carey, John. Looking for Lessons from Loons. National Wildlife. Vol 34 No. 5. Aug/Sept 1996. p. 16.

Drennan, Susan Roney. Loons. Audubon Vol 93. July/Aug 1991.

McIntyre, Judith W. Moonlight Cantata. Natural History May 1992.

National Geographic Society. 1996. Field Guide to the Birds of North America. Second Edition. National Geographic Society, Washington DC.

Rodriguez, Roberto J. Gavia immer [Common Loon; Great Northern Diver. http://www.oit.itd.umich.edu/bio/doc.cgi/Chordata/Aves/Gaviiformes/Gaviidae/Gavia_immer.ftl. 7/29/97.

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