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.
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Loons may be considered pests by commercial fishermen, who see them as competitors
Loons are aesthetically pleasing to observe in the nature and they are well known for their distinctive calls, which commonly occur at night.
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.
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.
Biogeographic Regions: nearctic (Native )
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
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.
Other Physical Features: endothermic ; bilateral symmetry
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.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
The Pacific loon, or Gavia pacifica, is part of the Gaviidae family and is one of the most abundant loons in North America. Males are slightly larger than females, but overall length for both sexes is between 58-74 cm, with a wingspan of 110-128 cm, and a weight between 1000-2500 g. (All About Birds 2017). G. pacifica’s body is stout and duck-like in structure. The nape, especially in breeding plumage, is grayer in contrast with the back, which is blacker, indeed blacker than other loons. During breeding season, the back is interrupted with patches of white. The bird’s flanks and underwings are snowy white (Russell 2002). Differences between the Pacific loon and the Common loon (Gavia immer) are that the Pacific loon is slightly smaller and its bill is straighter, thinner, and blacker than that of the Common loon (Alden 1998).
The native range of G. pacifica includes Alaska, Canada, and the West coast of the United States However, this bird has a very wide range and can be seen all around the Pacific Ocean including in Russia, Japan, Mexico and Korea. Breeding occurs on and around freshwater lakes in the arctic tundra, where G. pacifica spend the summer months (All About Birds 2017). The habitat that is ideal for G. pacifica is the ocean and associated bays and estuaries, where they winter and also rest during migration (Alden 1998).
The behavior of G. pacifica is sociable and they move in large numbers (in the thousands) when food is plentiful. During mating season, they are heavily aggressive and very territorial. They are very defensive of their nesting territories and have been observed to kill harmless birds like ducklings that come close to their nests (Kaufmann 2017). G. Pacifica hunts for its food by diving, propelled mainly by its feet, pursuing fish, crustaceans, and insects. Its diet varies seasonally -it is known to feed on plant material and mollusks during its breeding season, while mostly eating small fish during the winter (Kaufmann 2017).
After a ritualized courtship that includes bill dipping and splash diving from both the male and female. G. pacifica mate for life and have an average generation length of 9.8 years (BirdLife International 2016). Nests are made on the ground and can be identified by a simple depression or dip with scant lining. If the nest is formed near water however, it will typically be bowl shaped and filled with grasses and aquatic plants. G. pacifica raises one brood per year (All About Birds 2017). Numbers of G. pacifica are stable; however they are vulnerable to pollution, especially in offshore wintering areas (Kaufmann 2017).
The Pacific loon or Pacific diver (Gavia pacifica), is a medium-sized member of the loon, or diver, family.
The Pacific loon, previously considered conspecific with the similar black-throated loon, was classified as a separate species in 1985. The genus name Gavia comes from the Latin for "sea mew", as used by ancient Roman naturalist Pliny the Elder.[2] The specific epithet pacifica is Latin for the Pacific Ocean, the term meaning "peaceful".[3]
The phylogeny of this species is debated, with the black-throated loon and the Pacific loon traditionally being considered sister species, whereas a study using mitochondrial and nuclear intron DNA supported placing the black-throated loon sister to a clade consisting of the Pacific loon and the two sister species that are the common loon and the yellow-billed loon. In the former phylogeny, the split between the Pacific loon and the black-throated loon is proposed to have happened about 6.5 million years ago.[4]
Breeding adults are like a smaller sleeker version of common loon. They measure 58–74 cm (23–29 in) in length, 110–128 cm (43–50 in) in wingspan and weigh 1–2.5 kg (2.2–5.5 lb).[5] They have a grey head, black throat, white underparts and chequered black-and-white mantle. The black throat has purple reflections. Non-breeding plumage is drabber with the chin and foreneck white.[6] Its bill is grey or whitish and dagger-shaped.
In all plumages, lack of a white flank patch distinguishes this species from the otherwise very similar black-throated loon. The Pacific loon can be differentiated from the red-throated loon in winter by the latter's paler look, the fact that the red-throated loon has less of a contrast between both the crown and hindneck and the throat, and the bill that looks to be upturned.[6]
Like other gaviiformes, the Pacific loon's legs are located towards the back of its body making it difficult for it to walk on land. The leg placement helps the loons efficiently forage for food underwater. The physiological structure of the Pacific loon makes taking off from land practically impossible, and the loon requires 30-50 yards on the water to successfully attain flight.[7] This distance requirement for takeoff limits the number of lakes the Pacific loon can realistically breed and forage on.
The Pacific loon most actively calls in the spring and summer and has a wide range of calls. When feeding, the Pacific loon may produce an “ark”-like vocalization, a sharp, short call. Additionally, the Pacific loon has a call similar to that of its relative the common loon, it is a loud, eerie, oo-loo-lee wail or yodel that can travel for miles and is typically heard during the loon's breeding season. The loons can also make short and harsh “kok-kok-kok-kok” calls along with a range of other smaller cackles, growls, barks, and clucking noises.[6][7]
The Pacific loon breeds on tundra lakes, and winters in the open ocean or other large bodies of water. It breeds primarily in northern Canada and eastern Siberia, and winters along the Pacific coast of North America.[8]
Unlike other loons/divers, this bird may migrate in flocks. It winters at sea, mainly on the Pacific coast, or on large lakes over a much wider range, including China, Japan, North Korea, South Korea, United States and Mexico. It has occurred as a vagrant to Greenland, Hong Kong, Great Britain, Spain, Finland and Switzerland (Dec 2015).[9]
The Pacific loon constructs its nest on the ground near deep lakes. This nest is made out of piled-up vegetation.[10]
This loon lays a clutch of one to two light buff or green eggs with brown spots of various sizes. These eggs typically measure 76 by 47 millimetres (3.0 by 1.9 in). Although the eggs are laid a few days a part, they can usually be seen to hatch at intervals not more than a day. Incubation lasts 23 to 25 days.[10]
Socially monogamous Pacific loons have been found to have high territory retention rates (0.92) indicating that the loons are able to successfully defend their nesting lake from other loon pairs or individuals who may be trying to move in. Furthermore, males have a greater success at territory retention than females, but no evidence suggests that this difference is attributed to size but is rather due to fighting ability or familiarity with territory.[11]
Pacific loons prospecting for a new lake frequently visited lakes that were already occupied, this along with high retention rates of lakes indicates that the loon population in Northern Alaska may be saturated. The Pacific loon has also been known to be very aggressive, engaging in interspecific killing of both hatch year and after hatch year individuals who intentionally or accidentally approach the loon's nesting area.[12]
A pair of Pacific loons will defend young as a parental unit in which one parent protects the nest or fledglings while the other parent aggressively attacks the perceived threat. If the threat is another animal on the water, the attacking loon will extend its head and neck in an aggressive manner and dive under the threat in an attempt to stab it with its beak as it resurfaces.[13][12] Pacific loons are so aggressive, they have even been observed displaying threatening body language towards passing airplanes in Alaska.[13]
This species, like all divers/loons, is a specialist fish-eater, catching its prey underwater. It also forages in groups, usually swimming under schools of fish and forcing them up towards the surface.[10] It does, although, generally feed closer to the shore than other loons.[6]
The Pacific loon population is currently increasing and is spread over a wide range of approximately 15,700,000 square kilometers.[14] Current efforts of conservation are focused around loon population monitoring and maintaining accurate counts of populations and breeding behaviors. A recent in depth study of the Pacific loon population in the Western Alaskan Arctic found that the population of the birds there is actually ~1.5-2.0 times larger than previous aerial surveillance had indicated. The study indicated potential encroachment upon the National Petroleum Reserve in Alaska (NPRA), one of the Pacific loons primary breeding grounds, by natural gas and oil companies as a potential threat to Pacific loons.[15]
One harmful environmental pollutant to the Pacific loon population is heavy metals like mercury, which can be observed in their habitat as a result of legacy mining in the areas the loons migrate through and hunt in. It has been shown that elevated levels of mercury in the environment poses a significant health risk to avian piscivores like the Pacific loon.[16] Mercury is up-taken by small fish which is a primary source of food in a loon's diet. When a loon eats the fish it will incorporate the mercury from the fish into its body, which can cause adverse health effects.
Additionally, it has been shown that nest visits from researchers and capture events can have a significant impact on the survival rates within Pacific loon nests. When investigators capture Pacific loons while they are breeding or incubating eggs regardless of how close they are to the nest at the time of capture, the survival rates of the eggs decrease.[11] This is most likely due to the fact that Pacific loons nest in a traditionally remote part of Western Alaska and are not typically accustomed to human interaction of any form. The lowered survival rate of the loon's offspring when a parent is captured or the nest is visited indicates that the population could face severe consequences from encroaching human contact.
Reports also exist of Pacific loons ingesting polluted plastic, a problem that is becoming an increasingly high concern among avians in Canada and across the globe. Luckily, the diving foraging behavior of loons keeps them at a relatively low risk of death from overconsumption of plastic, as most of the polluted debris exists floating on the surface of the water rather than in the depths.[17]
In Alaska The Pacific loon or Pacific diver (Gavia pacifica), is a medium-sized member of the loon, or diver, family.
