The Loon's Family and Social Life
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 often switch mates if their previous mate does not return in the spring or is displaced by a rival loon during the 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 loon family moves to a “nursery” area to raise their young and they 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.