Merlin

Pacific Loon Life History

Habitat

Habitat Lakes and Ponds

Pacific Loons nest along the margins of freshwater lakes in tundra and taiga habitats of the far north. These are usually in flat lowlands but sometimes in foothills. Ponds are large, at least several acres in extent, in order to provide enough open water for landing and especially for take-off. In tundra habitats, the lake edges have vegetation such as pendant grass, water sedge, Lyngbye's sedge, mare's tail, bur-reed, marsh five-finger, and pondweed. In the breeding season they sometimes forage in the lakes where they nest (especially when feeding chicks), but they usually fly to nearby lakes, rivers, or marine waters to feed. During migration, Pacific Loons may gather in places where ocean currents concentrate prey, such as areas of upwelling or tidal bores, or places where fish have gathered to spawn. Wintering Pacific Loons concentrate in channels, straits, bays, or estuaries with abundant prey, but they chiefly frequent nearshore ocean waters with sandy rather than rocky bottoms.

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Food

Food Fish

Pacific Loons eat mostly small fish, which they hunt below the water’s surface, swimming agilely with the feet to capture prey in the bill. Before diving, they often dip their heads underwater to look around for fish, as Common Loons do. In the ocean they sometimes hunt in loose groups, and they also forage in mixed-species flocks of auks, gulls, loons, and cormorants, with each species exploiting the schooling fish in a different manner. Gulls often try to steal fish from the loons if the loons have not swallowed the prey by the time they return to the water’s surface. In Japan, fishermen describe seeing Pacific and Arctic Loons forcing small fish into a “bait ball,” from which the birds can more easily extract individual fish. During the breeding season, Pacific Loons often forage in shallow nesting ponds, where they may take some prey without diving and sometimes stir the sediment with the bill, trying to locate prey. At this season, they eat fish, snails, mollusks, insect larvae, and zooplankton such as amphipods. Common prey include arctic grayling, ninespine stickleback, fairy shrimp, tadpole shrimp, water boatmen, caddisfly larvae, dragonfly larvae, water fleas and their eggs, and chewing lice. Some birds also eat seeds and plant fiber at this time of year. Pacific Loons also consume pebbles, as other loons do. These pebbles (usually more than a dozen) remain in the gizzard, where they help break down the food. In the nonbreeding season, small fish form the bulk of the diet, especially Pacific herring, shiner perch, surfperches, Pacific sandlance, northern anchovy, and medusafish. Pacific Loons also eat small squid.

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Nesting

Nest Placement

Nest Ground

Male and female select the nest site together. Nests are set on the edge of an island in a lake or on the lakeshore, directly on the ground.

Nest Description

Both male and female arrange mud and dead aquatic vegetation to make a basic oval-shaped nest on land; this process requires only a few hours. Some nests are built in the water, and so the pair must work for a full day or two to build a 15- to 20-inch mound of material. The bowl of the nest (which holds the eggs) measures on average about 9 inches across and 1 inch deep, but varies widely. Some pairs even build floating nests.

Nesting Facts
Clutch Size:1-2 eggs
Egg Description:

Variable shades of buff, brown, and olive-green.

Condition at Hatching:

Downy and active; leaves nest within one or two days.

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Behavior

Behavior Surface Dive

Pacific Loons spend much of the day foraging, resting, and flying. They are very strong fliers but cannot take flight in calm conditions without a large area of open water (at least 100 feet) to use as a runway: they flap and patter along the water before becoming fully airborne. They also swim and dive strongly, using their feet for steering and propulsion. They swim with their wings closed, unlike auks and shearwaters. As soon as males arrive on breeding grounds, they select a nesting lake, which they defend as their territory for the entire breeding season. Often, Pacific Loons arrive in nesting areas before these lakes have thawed, and so their claim only begins when open water appears. On larger lakes, multiple pairs defend non-overlapping territories. Both males and females may confront trespassers with loud calls, threat displays, and outright attacks. When pairs use smaller lakes, they may defend two or even three adjacent lakes as their territory. Male and female share incubation and chick-rearing duties. Mated pairs and groups of Pacific Loons can be seen displaying during the breeding season. The female of a pair invites the male by climbing onto the edge of the lake, bowing the head, and raising the tail. Group displays include nesting birds, or failed breeders, gathering into small flocks, often late in the day, and dipping the bill or diving in synchrony, usually accompanied by vocalization. Failed breeders may move from lake to lake, sometimes coming into conflict with pairs of loons on each lake. During migration and winter, Pacific Loons often gather in very large, loose flocks, but they often forage alone or in pairs as well.

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Conservation

Conservation Low Concern

Pacific Loons are abundant, but there is little information on their population trends. Spring migration counts in California showed a sharp decline between 1979 and 1996; however, there are no comparable data from the breeding grounds. Partners in Flight estimates a global breeding population of 840,000 and rates the species a 10 out of 20 on the Continental Concern Score, indicating a species of low conservation concern. Pacific Loons are still hunted (and their eggs gathered) in native communities of the Arctic, but the extent and impacts of these practices are not known. Net fishing can kill Pacific Loons, especially in commercial gill-net fishing. Oil and gas development has the potential to damage Pacific Loon habitat in their tundra nesting grounds and along shorelines.

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Credits

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.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

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

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