Red-throated Loon Life History

Habitat

Habitat Lakes and Ponds

Red-throated Loons breed in rugged tundra and taiga wetlands in both lowlands and highlands, up to about 3,500 feet elevation. Their ability to spring into flight without first pattering on the water (as other loons have to do) permits them to use small ponds for nesting. They do use larger lakes in places where larger loons are absent. In migration, they fly along ocean shorelines and also along the shores of large lakes (such as the Great Lakes), but their precise migration routes are not known. Foul weather sometimes grounds migrants in places where they would not otherwise land, such as rivers and small lakes in interior North America. Wintering birds are found only in shallower marine waters near land, and in major estuaries and sounds. They are very rarely seen far out to sea.

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Food

Food Fish

Red-throated Loons eat a variety of fish, leeches, copepods, crustaceans, mollusks, squid, polychaete worms, and aquatic insects. Among fish they eat herring, capelin, brook trout, stickleback, sculpin, tomcod, arctic char, cod, and sandlance. When breeding, they forage away from nesting areas and nursery ponds, usually in larger lakes and rivers, often in estuaries. Red-throated Loons hunt prey by diving underwater, swimming by kicking with the legs and then grasping prey with the bill. They often locate prey first by dipping their head underwater and looking around as they rest on the water’s surface.

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Nesting

Nest Placement

Nest Ground

Males select the nest site, usually in wetlands at the edge of a shallow, small pond or on a small island in the pond. In the high arctic, they nest on larger ponds. Nests are always built on vegetation, not on rocks.

Nest Description

Both male and female build the nest, either on the shoreline or in shallow water near it. Nests are mounds of moss, decayed vegetation, grasses, sedges, and mud, sometimes lined with dry grass, gathered from the immediate vicinity of the nest and formed with the feet and body. In some cases, no nest material is used, just a depression in the vegetation. Nests average about 18 inches across and about 3 inches above waterline; the interior depression averages 9.5 inches across and 1.6 inches deep.

Nesting Facts
Clutch Size:1-2 eggs
Number of Broods:1 brood
Egg Length:2.7-3.0 in (6.82-7.67 cm)
Egg Width:1.7-1.8 in (4.41-4.55 cm)
Incubation Period:24-31 days
Egg Description:

Elongated, with variable color ranging from brown to olive, with blotches or speckles.

Condition at Hatching:

Downy and active; capable of swimming within 12 to 24 hours.

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Behavior

Behavior Surface Dive

Red-throated Loons are monogamous, but little is known about the longevity of their bonds or where and how pairs form. Pairs use displays to defend territories (chiefly the nesting pond and nest vicinity) against intruders, including humans. Adults may raise or lower the neck, splash-dive, slap the water with their feet (recalling a beaver tail-slap), to warn intruders, or may rush across the water with wings partly open and head extended, in threat. Pairs are often observed in what researchers call a “plesiosaur posture,” in which they raise the body out of the water, extend the neck, raise the wings, and tip the bill downward. A similar display known as the “penguin posture” involves raising the body vertically, stretching out the neck, and pointing the head and bill downward. Males and females perform these displays typically at other Red-throated Loons who intrude on their territory. Both parents tend and feed the young. After the young birds are several weeks old, they sometimes move to a different pond or lake. Adults and young move toward coastlines in preparation for migration, which occurs at least partly at night. Daytime movements of many thousands are often seen along marine coasts. When foraging over the ocean, this species is highly mobile and may dive for prey, much like the Northern Gannet, which occupies a similar niche in winter, though gannets can consume larger prey and forage farther from shore.

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Conservation

Conservation Low Concern

Red-throated Loons occur across North America, Europe, and eastern Asia. Partners in Flight estimates a global breeding population of 260,000. The group rates the species a 10 out of 20 on the Continental Concern Score, indicating it is a species of low conservation concern. In the late twentieth century, scientists recorded long-term population declines of about 50%, in some cases possibly due to lake acidification. These declines appear to have stabilized. Oil spills, hunting (in northern Canada and parts of Europe), degradation of marine habitats, industrial activity in breeding areas, overfishing of prey, and entanglement in fishing nets all pose threats to Red-throated Loons.

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Credits

Barr, Jack F., Christine Eberl and Judith W. McIntyre. (2000). Red-throated Loon (Gavia stellata), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

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