Facts about Loons

Life Cycle

Q. How long is the normal lifespan of a loon?

No data is available on how long it is possible for a common loon to survive; is probably close to the Arctic loon, 25 - 30 years. The oldest known age of a banded loon was 13 years 1 month.

Q. What do loons need to raise young successfully?

Dr. Judith McIntyre says loons must have clear water, a good supply of fish, a variety of bottom types and depths, nesting islands with steep drop-offs and good views of the territory, and quiet, protected places to raise chicks. Clear water is essential for seeing fish and chasing them down. It takes a TON of fish to feed two loon adults and two chicks over the summer, so a good supply of fish is critical. The wider the variety of bottom types and depths, the greater the variety and supply of fish. A nesting island with a steep drop off allows loons to slip into the water quickly when confronted with a predator. The good view of the territory is important to detect predators before it's too late. The quiet, protected place is important so they can avoid predators to begin with.

Q. Do all the loons return to their summer breeding lakes in the north?

No. Loons take about 3 years to sexually mature before they molt into the definitive breeding plumage and return to the north to nest.

Q. Do loons have the same mate from year to year?

Dave Evers: Loons are actually more attached to their nesting lake than to a specific loon partner. In the past many people and researchers believed that loons mated for life, but recent studies have shown that loons do switch partners from year to year. In fact, Dr. Walter Piper has been studying loons in the Rhinelander, Wisconsin area and has found that loons even switch mated within nesting seasons. For example, if the loon pair's first nest fails, the female loon may renest with another adult male bird the same season.

Q. How do loons mate?

Loons usually mate on the nest site. It is a quick process. The male loon will approach the nest site and give a quiet call. If the female is interested, she will approach and climb onto the nest. The male will climb on top of her and copulation occurs. It only takes a few moments and then he drops into the water. They sometimes call after copulation.

Q. How big are a loon's eggs?

Loon eggs are elliptical in shape, averaging about 8.7 cm in length and 5.5 cm in width. That makes them about the size of one and a half tennis balls. Loon eggs weigh 125-180 grams, or about 3.5 % of the mother's body weight.

Q. Why do loons lay only two eggs?

The first answer is that loons only lay two eggs because their body size and physiology (how their body works) does not allow them to produce any more than that. The eggs are big, and it takes a lot of energy to produce two of them! In order to gain that energy loons have to eat a lot of fish and NOT spend time chasing off intruders or other activities that use up their energy. The other answer is that loons live for a long time. It is believed that loons can live to be 30 years old, which is a long life compared to most birds. Animals that have long life spans produce low numbers of young. This prevents overpopulation and exceeding the carrying capacity of the habitat.

Q. What color are loon eggs?

A. Loons lay 2 big, greenish-brown eggs with a speckling of black markings. This usually matches their muddy nests that are constructed of different plants, sticks, and debris. Because their nests are on a shore and often have little or no cover from above, the color and speckling help provide camouflage to protect them when eagles or gulls fly over.

Q. Why are the eggs laid and hatched on different days?

A female loon has only one working ovary, so her body can produce only one egg at a time. Just producing one loon egg takes a lot of energy! She lays her eggs 1-3 days apart, but the eggs usually hatch a little closer together than the time they were laid. In years with poor fishing or on far northern lakes that don't have a lot of small fish, the eggs are laid farther apart than in years or places with abundant fish.

Q. Why do young loons fight?

Young loons fight to establish a "pecking order" or dominance between the chicks. Loon chicks hatch 24 hours apart and often the first chick to hatch is slightly bigger and is dominant. This means that when the parents bring food the bigger chick is more likely to get fed. While this may seem cruel to the smaller "brother or sister" it is a survival mechanism. If the loon parents don't bring enough food for both chicks the larger dominant chick is likely to survive rather than both chicks being weaker and more vulnerable.