Great Northern or Common Loon, Gavia immer

Great Northern Loon on NC coast in winter 2/1/11            ©Greg Patch

Great Northern Loon on lake in Canada during summer      ©Matthew

http://www.loon.org/about-loons.php

Loons, like ducks, geese, cormorants and grebes, are waterbirds, but they are classified separately by scientists.  Their closest living relatives are penguins and a group of birds called the “tube-nosed swimmers” (including albatrosses, petrels and shearwaters).

North America is home to five species of loons, including the Red-throated Loon (Gavia stellata), Pacific Loon (Gavia pacifica), Arctic Loon (Gavia arctica), Yellow-billed Loon (Gavia adamsii) and Common Loon (Gavia immer).  The Common Loon is the most widespread and well-known species, and the only one that breeds as far south as New Hampshire.

In spring, loons arrive on northern lakes as soon as the ice thaws. Loons are territorial birds, and a mated pair of loons will defend an area of water from other loons. Small lakes, generally those between 5 and 50 ha, can accommodate one pair of loons. Larger lakes may have more than one pair of breeding loons, with each pair occupying a bay or section of the lake.

Until recently, loons were thought to mate for life. However, banding loons to allow the identification of individuals has shown that loons will sometimes switch mates after a failed nesting attempt, sometimes even in the same breeding season. Courtship and mating are a quiet time, with the pair swimming and making short dives together. Eventually, the male leads the female to a suitable spot on land to mate. Nest building then begins.

Loons build their nests close to the water, often on a small island, muskrat house, half-submerged log, or sedge mat. The same sites are often used from year to year. Loons will use mud, grass, moss, pine needles and/or clumps of mud and vegetation collected from the lake bottom to build a nest. Both the male and female help with nest building.

Usually one or two eggs are laid in late May or June, and incubation of eggs generally lasts 26-28 days. If the eggs are lost, the pair may renest, often in the same general location. Loon chicks covered in brown-black down appear on the water in late June or July. Chicks can swim right away, but spend time riding on their parents' backs to rest, conserve heat, and avoid predators such as large fish, snapping turtles, gulls and eagles. After their first day or two of life, the chicks do not return to the nest.

Chicks are fed small food items including minnows, insects and crayfish caught by their parents for the first few weeks of life, and up until eight weeks of age, the adults are with them most of the time.  Gradually, the chicks begin to dive for some of their own food, and by 12 weeks of age, the chicks are providing almost all of their own food and are able to fly.  By the fall, the young are able to look after themselves.  Adult loons generally migrate to the ocean to overwinter in October or November.  The young follow on their own, often just before ice-in of their natal lake.  They will not return to their natal lakes until they are 26 months old or older, and might not breed until they are six or seven years old.

Loons are generally solitary birds.  However, they will sometimes gather for short periods in small groups of up to 20 birds in late summer and fall, and can sometimes be found in groups on their ocean wintering grounds.