Courtship, Nesting, and Raising Chicks
Loons are long-lived, and territorial, often returning annually to the same area on the same lake to breed. In the spring, males migrate back to their breeding lakes before the females to establish and set up a territory for nesting. Banding studies have shown that loons do not mate for life, and occasionally do switch mates or territories. When one loon dies, the remaining member of a pair will find another mate. Additionally, another loon or pair may intrude on a territory, and one or both birds of the original pair may be displaced.
Courtship behavior is very subtle and quiet, including side-by-side swimming, bill dipping, circling, and soft hoots between the pair. Nests are usually situated in vegetation on the edge of an island, bog mat, log, or even a large rock, adjacent to deep water, enabling a loon to slip into the water virtually unnoticed if danger threatens. Their nests vary from a shallow scrape to a large (~1-2 feet across) bulky bowl of vegetation.
Incubation usually begins in May or early June, although it may occur later, particularly if the first nest fails and the birds renest. One or two (rarely three) large (~3-4 inches long) oval eggs are laid. The eggs are olive-green to brown in color and often have brown spots. They are well camouflaged in the nest if the parent goes off to eat or bathe.
Incubation is shared by both parents for ~26-30 days until the chicks hatch. If an incubating bird is disturbed by a predator, another loon, or a human, it may hurriedly scramble off the nest and wingrow across the water, possibly accidently knocking an egg off the nest in their hurry to get away. Alternatively, some birds are “stickers” and will remain on the nest until they absolutely have to move. If they feel threatened, they may freeze in a “hangover” position, which enables the bird to hide itself in the vegetation, and minimize the chance that a predator would see it. Loons can also easily slip into the water from this position, since their head is very close to the water. If you observe a loon in a hangover , it is likely that you might be too close to the nest for the bird’s comfort. Try moving away (you might have to move a long ways – even to the other side of the lake) and looking through binoculars. After a while, you should see the loon resume a normal incubating position with its head up in the air, calmly looking around.
The chicks are little black, downy “puff-balls” when they first hatch. The first egg laid hatches first, and that chick is a little bigger than the other chick(s). The chicks establish a dominance hierarchy by fighting the first day or two of their lives. The larger chick has the advantage and becomes the dominant chick, getting fed first by the parents. Sometimes, if food is limited, the dominant chick grows at a much faster rate than the other chick(s) because it gets fed more and receives more care from the parents. Occasionally the younger chick(s) dies because it is not getting enough food or care.
Once the chicks hatch, they ride on their parents’ backs for the first two-three weeks of life. Back riding protects them from underwater predators and keeps them warm when they snuggle into the soft down under their parent’s wings. The chicks are initially raised in a sheltered, "nursery" area of the lake, where they grow rapidly, changing to a dusky brown down at three-four weeks of age. The chicks gradually expand their use of their territory over the next 2-3 months as their gray juvenile plumage replaces the down.
The primary flight feathers are last to develop, and, although they are the size of adults, the chicks are not able to fly until they are 11 to 12 weeks of age. Loon chicks usually leave their natal lake after their parents, migrating to the coast for the winter, where they will spend the next two to four years before returning to the breeding grounds. Loons are usually six to seven years old before they establish a breeding territory with their first mate.