Common Loon (Gavia immer)
The Common Loon also know as the Great Northern Loon in North America is known in Eurasia as the Great Northern Diver. The eerie calls of Common Loons echo across clear lakes of the northern wilderness. You’ll find them close to shore on most seacoasts and a good many inland reservoirs and lakes. Common Loons are powerful, agile divers that catch small fish in fast underwater chases. They are less suited to land, and typically come ashore only to nest.
Adults can range from 61 to 100 cm (24 to 39 in) in length with a 122–152 cm (48–60 in) wingspan. The weight can vary from 1.6 to 8 kg (3.5 to 18 lb). On average, a Great Northern Loon is about 81 cm (32 in) long, has a wingspan of 136 cm (54 in), and weighs about 4.1 kg (9.0 lb).
Breeding adults have a black head, white underparts, and a checkered black-and-white mantle. Non-breeding plumage is brownish, with the chin and foreneck white. The bill is black-blue and held horizontally. The bill colour and angle distinguish this species from the similar Yellow-billed Loon.
The Common Loon breeds in North America, Greenland, Iceland, and Great Britain. They winter on sea coasts or on large lakes of south Europe and the United States, and south to north western areas of Africa.
Loons, like all divers, is a specialist fish-eater, catching its prey underwater, diving as deep as 60 m (200 ft). Freshwater diets consist of pike, perch, sunfish, trout, and bass; salt-water diets consist of rock-fish, flounder, sea trout, and herring.
Male and female build the nest together over the course of a week in May or early June, making a mound out of dead plant materials such as sedges and marsh grasses that grow along the lake’s edge. Then one of the loons crawls on top of the mound and shapes the interior to the contours of its body. The finished nest is about 22 inches wide and looks like a clump of dead grasses by the edge of the water.
The male selects the nest site. Loons nest in quiet, protected, hidden spots of lakeshore, typically in the lee of islands or in a sheltered back bay. Loons can’t walk well on land, so nests are built close to a bank, often with a steep dropoff that allows the bird to approach the nest from underwater. They also use artificial nesting platforms, which people have offered as alternative habitat on lakes with extensive shoreline development. Many times a nesting pair of loons will reuse the same site the following year, refurbishing their old nest instead of building a new one.
References: Wikipedia, Cornell Lab of Ornithology