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LOONS. Becky Marischen. Taxonomy. GAVIIFORMES GAVIIDAE Gavia stellata Red-throated Loon Gavia arctica Arctic Loon Gavia pacifica Pacific Loon Gavia immer Common Loon Gavia adamsii Yellow-billed Loon. Life History. Loons are among the oldest groups of birds still living today.
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LOONS Becky Marischen
Taxonomy • GAVIIFORMES • GAVIIDAE • Gavia stellata Red-throated Loon • Gavia arctica Arctic Loon • Gavia pacifica Pacific Loon • Gavia immer Common Loon • Gavia adamsii Yellow-billed Loon
Life History • Loons are among the oldest groups of birds still living today. • Closest living relatives are penguins and the tube-nosed swimmers (Albatrosses and Shearwaters). • All five species are restricted to the northern hemisphere and all are migratory.
General Characteristics • Appearance • All species have a red pigment in the retina that filters light when loons dive beneath the water's surface and allows for sight • Sexes alike, males tend to be larger • Grayish non-breeding plumage and a striking alternate plumage
General Characteristics cont. • dagger-like bills • feed primarily on small fish also known to eat aquatic vegetation, insects, mollusks, and frogs • lobed feet set far back on the body - are very clumsy on land. • Diving • loons have solid bones • the extra weight helps them dive • Can also expel air out of their feathers • Use feet for propulsion, wings for turning • have been trapped in fishing nets 240 feet below the surface • can stay underwater for several minutes
General Characteristics cont. • Flight • Because of their large size and weight, loons require about 1/4 mile of lake surface to become airborne • Once airborne, loons are powerful fliers • Pilots have checked them flying at speeds up to 80 mph
Vocalization • Loon calls have been identified into four classifications: Wail, tremolo, yodel and hoot. • The wail is perhaps the call most frequently heard. • The tremolo signals alarm or annoyance, frequently given after a disturbance. • The yodel is given only by males, it serves as an aggressive territorial proclamation. • The hoot is used as a contact call. • The vocalizations differs among species. • The red-throat erupts into a rapid quacking, and the pacific loon has a wailing siren of a voice, an ascending whistle that it shortens to a piercing scream when startled. • Loons can be heard day and night during breeding, but they are nearly silent in the winter
Behaviors • The "penguin dance“ is a sign of extreme agitation. This is usually a territorial behavior. • generally combined with frantic calls and is one of the last available defensive actions
Breeding Habitat • A suitable lake is clear and large to provide territories typically between 100 and 200 acres • Must have an adequate supply of fish • It must also have islands or inlets suitable for nesting • Relatively free from human disturbance
Loons are territorial and generally one pair is found per lake, except for large bodies of water. Courtship consists mainly of head dipping and shallow dives. In spring, loons are frequently observed chasing each other across the surface of a lake. This is primarily territorial behavior, not courtship ritual. Loon pairs mate for life, however, banding studies have shown that loons will sometimes switch mates after a failed nesting attempt and even between nesting attempts in the same season. They return every year to the same area to breed. often reuse the same nest each year Both the male and female participate in nest building and take turns incubating. Breeding Behavior
Breeding Behavior cont. • The nest is a loosely formed mound consisting of reeds, sticks, grasses and muddy vegetation with a slight hollow in the middle. • Because of their difficulty moving about the land, loons build nests within a few inches of water. • When a nesting loon is disturbed, it slips off the nest and submerges to keep the location of its nest unknown. • Incubation period is 23-31 days • Clutch size 1-3 • Usually only one chick survives to migration.
Breeding Behavior cont. • The young are precocious and leave the nest within a day or two. • Chicks ride on their parents' backs more than half the time in their first week of life. • this help keeps them dry, warm, and safe from predators • loon chicks must be fed by their parents • their diet consisting mostly of small food items; snails, small fish, crayfish, minnows, and some aquatic vegetation • about 8 weeks the chicks begin to dive for some of their own food • by 11 or 12 weeks of age, the chicks are providing almost all of their own food • sometime in the third month the chicks learn to fly • Immature loons resemble adults in winter plumage.
Migration and Population • Loons migrate in loose aggregations and roost together in flocks of as many as several hundred birds. • Adults migrate first and chicks follow later • The chicks will not return to their natal lakes until they are three or four years old and are ready to breed. • The abundance and even in some cases the geographical ranges of these species are still poorly known. • Loons are widely distributed, making it difficult and expensive to survey populations.
Red-throated Loon: Gavia stellata As its name implies, the red-throat has a triangular throat patch of vivid, rusty red.
Red-throated Loon: Gavia stellata • Red-throated loons, Pacific loons, and arctic loons are smaller varieties and readily distinguished from their larger cousins by gray rather than black heads • The Red-throat is the smallest, slightest of the divers • stands at 53-69 cm and its wingspan ranges from 106-116 cm • This loon species is unique in being able to take off from land. • The Red-throated Loon is an uncommon migrant in Kentucky. Recorded mostly in larger bodies of water such as the Green River Reservoir.
Red-throated Loon: Gavia stellata • Range • Breeds far into the high Arctic, and winters mainly on the northern coasts of the Atlantic and Pacific. Also in the Great Lakes. • spends the winter along the Pacific coast from the Aleutian Islands to Baja • Nest failures due to predation are more common than those due to human disturbance, because their North American range in does not overlap much with where humans live.
Arctic Loon Gavia arctica Arctic loons have a greenish-black throat, but otherwise look similar to Pacific loons.
Arctic Loon Gavia arctica • The Arctic Loon breeds onthe tundra, and is usually found only on the west coast in winter. It rarely wanders eastward in the winter, and into the Great Lakes region. • They are found in extreme western Alaska (Cape Prince of Wales). • The Arctic Loon is a rare visitor to the Great Lakes, and is only seen there in winter.
Pacific Loon: Gavia pacifica The throat of the Pacific loon is purplish black while its black back has bars and spots of white, similar to the common and yellow-billed.
Pacific Loon: Gavia pacifica • Pacific loons until recently were considered a subspecies of Arctic loon. • Their average length is 66 cm. • The Pacific Loon is a very rare vagrant in Kentucky. It is known in the state from fewer than 10 records. • The Arctic Loon breeds on the tundra, and is usually found only on the west coast in winter. It rarely wanders eastward in the winter, and into the Great Lakes region.
Yellow-billed Loon: Gavia adamsii • Range • Breeds from northern Alaska and northern Canada east nearly to Hudson Bay. • Winters along coast from Alaska south to British Columbia, and occasionally to California. Distribution of Yellow-billed Loon in Canada
Yellow-billed Loon: Gavia adamsii • The yellow-billed is the largest of the loons (30-36 inches long) and one of the largest diving birds in North America. • The yellow-billed loon is similar to the common loon, but it has white spots on its back and a straw-yellow bill even in winter. • It is the least abundant of the five loons that nest regularly in North America. • Compared to other loon species, the yellow-billed loon is far more restricted to the Arctic. It has an almost circumpolar distribution, but is not common anywhere in the world.
Common Loon: Gavia immer Breeds in North America from Alaska and southern Baffin Island, south to northern United States; also in Greenland and Iceland. Winters along the coast from southern parts of its breeding range south to the Gulf of Mexico, and in parts of Europe.
Common Loon: Gavia immer • One of the larger loons about 70-90 cm in length and weighs on average 9 lbs, but ranges from 6-14 lbs • The Common Loon is the state bird of Minnesota and the national bird in Canada • The loon is the Canadian equivalent of the Bald Eagle. • The Common Loon has the most reliable information on population numbers of the loon species, this is because of its southern distribution and its overlap with human populations. • Common Loon populations in Canada have been estimated at between 250,000 and 500,000 individuals. • Estimated 15,000 loons in the Upper Great Lakes States of Minnesota, Wisconsin, and Michigan • comprise nearly three-quarters of the loon population outside of Alaska. • In Kentucky the Common Loon is common in large bodies of water in migration and uncommon to common in winter. • Usually seen in winter plumage
Management Concerns • Of the 27 killed by trauma • Seven individuals were shot • 9 died of injuries due to collisions with boats, cars, or power lines • 6 drowned in fishing nets • in 5 cases the source of the trauma was not determined • In 15 of 19 birds killed by lead poisoning a fishing weight was present in the gizzard. • All but one of the six loons dying of aspergillosis had some other serious disease condition as well. • At least 51 of 71 birds (72%) died as the result of trauma, entanglement or lead poisoning, all of which are consequences of human actions. • 1993, the Ontario Ministry of Natural Resources (OMNR) and the Canadian Cooperative Wildlife Health Centre (CCWHC)
Management Concerns: Disturbance • Human activities are largely responsible for the disappearance of loons from many lakes. • Development of shorelines and islands destroying nesting habitat. • Disturbance of loons, especially during sensitive nesting and chick-rearing periods, can reduce or wipe out loon populations. • More disturbances = more time away from incubating eggs • Pollution of lakes used by nesting loons can lead to accumulations of toxins in eggs and young and the loss of food for chicks and adults. • Loons are also susceptible to oil spills, especially on the winter range
Management Concerns: Acidity • Recent studies have indicated that loon nesting success and survival of young may decrease with increased lake acidity, the result of acid rain. • Acidity can result in decreases in fish and other foods, • This causes chicks on very acid lakes to starve. • Acidification of lakes may also increase the rate of methylmercury production by microbes in lake sediments and water, resulting in higher concentrations of mercury in the food chain.
Management Concerns: Mercury • A significant proportion of loons found dead in the United States and Canada have high concentrations of mercury in their tissues. • Canadian research has demonstrated that loons nesting near industrial sources of mercury pollution occupy few potential territories and lay few eggs, resulting in poor reproductive success. • Increased methylmercury concentrations in fish, the loon’s main food source, is the result of environmental mercury pollution, acidification, and flooding of forested land for hydroelectric development. These activities pose a threat to the health and reproductive success of loons in many locations throughout their range.
Management Concerns: Lead • Loons die of lead poisoning after eating fish with lead sinkers, and possibly after picking up discarded sinkers from lake bottoms. The lead is partially dissolved in the loon’s gizzard then absorbed into the blood and body tissues. • The absorbed lead causes nerve, kidney, and other tissue damage. • Abandoned or unattended fishing line and hooks also cause loon injury and death.
Management Concerns • To protect the loons on lakes used for recreation, boats should be kept well away from swimming birds, particularly when they are with chicks that are too young to dive or fly. • Some shoreline areas should be left undisturbed to accommodate loon nests, and boaters passing these areas should travel at speeds that do not cause wash. • Seaplanes should come and go as far from nesting areas as possible, taxiing to other parts of the lake. • Anglers have the responsibility of using non-lead sinkers and of ensuring that no hooks or lines are left unattended or abandoned.
