By Mary Hoff
You're at the lake, curled up cozy in your sleeping bag. The sky is just beginning to lighten in the east. Then you hear it: a long, haunting cry from out on the water. Woo -- oooo! Along with the tug of a fish on a line, the splash of water against the side of a boat, the whine of mosquitoes, and the sparkle of sunshine, the call of the common loon (Gavia immer) means summer in the land of 10,000 lakes.
April is a busy time in northern Minnesota. The ice is disappearing from long-frozen waters. Leaf buds are swelling on trees. High overhead, a few silhouettes dot the sky. Common loons are starting to arrive after a long flight from wintering areas near the Atlantic Ocean and the Gulf of Mexico.
SPLASH! A male loon hits the surface of a lake, spraying water all around. This is familiar territory for him: He hatched from an olive-brown egg on a nearby lake five years ago, and last year he raised two chicks of his own on this lake.
For a day or two, the loon swims around the lake by himself. He dives beneath the surface of the water and zooms like a torpedo in search of perch, bluegills, and other small fish to eat. Back on the surface, he calls loudly with a long, warbling cry, announcing to other males that this part of the lake belongs to him.
Then one day he hears another SPLASH! It is a female loon, his mate, back from her southern wintering place.
Few birds use sound to communicate in as many different ways as loons do. Scientists have categorized common loon calls into four main types. Each conveys a unique message.
HOOT: A loon gives a hoot -- a soft, short call -- to let other loons know where it is or to ask another loon where it is. A parent might hoot to its chick, or one of a pair to another.
TREMOLO: The wavering tremolo call -- sometimes called the loon laugh -- means a loon is excited or alarmed. Loons also use the tremolo when they fly over a lake to announce their presence to any loons there.
YODEL: Only male loons make this loud sound, which starts with three notes and ends with a couple of swinging phrases. They use it to defend their territory. Each male has a -"signature" yodel. Some people can recognize a specific loon by his yodel.
WAIL: The high, haunting wail helps loons to figure out where they are relative to each other. They call back and forth, using the location of the sound to move closer together.
Loons are protected by the federal Migratory Bird Treaty Act of 1918. This law makes it illegal to capture or kill loons and to gather, possess, or harm their nests, eggs, or feathers.
However, loons still face many threats. As more people build homes on lakeshores and fill the lakes with the sights and sounds of boating, loons are finding less privacy. Although loons can share a lake with humans, they need quiet, undeveloped areas in the spring for nesting.
Loons have other people problems too. Some die when they become tangled in fishing line or eat poisonous lead fishing tackle. Mercury from factories and power plants can pollute lakes and the fish that swim in those lakes. When loons eat those fish, they also take mercury into their bodies -- making it harder for loons to reproduce. Biologists are watching to make sure loons keep thriving in Minnesota. Since 1994 volunteers have helped count loons on more than 600 lakes around the state through the Department of Natural Resources Minnesota Loon Monitoring Program. To participate in this program, call 651-259-5120. Other volunteers watch loons at lakes they visit often and report to the Volunteer Loon Watcher Survey. To participate in this survey, call 218-828-2228.
The two loons look at each other with their bright red eyes. They talk to each other with soft hoots. They remember each other and the little loons they raised here the summer before.
After dancing and calling to each other, the loons mate. Then they begin to build a nest at the water's edge, piling grass, leaves, and mud into a circle the size of a bicycle tire. The female loon lays a speckled olive-brown egg in the center of the nest. The next day she lays another.
The two loons take turns sitting on the eggs to keep them warm and safe from crows, raccoons, and other predators. They turn the eggs often and add more twigs, reeds, and other vegetation to the nest. The incubating parent faces the water so that it can quickly dive away from the nest if a predator comes too close.
After almost a month, the parent loons hear a tiny tapping sound. One of the eggs cracks, and a soggy dark ball emerges. The next day the second chick breaks its way out of the other egg.
Shortly after hatching, the young loons are ready to swim. And that's a good thing because they will spend most of their lives in the water, not on land or in the air. Soon the family abandons the "high and dry" nest entirely.
At first the parents feed minnows and aquatic insects to their chicks. But by the time they are eight weeks old, the chicks are diving to find their own fish, leeches, and other food. As they travel around the lake, the loon chicks sometimes ride on a parent's back. This helps them stay warm and safely out of reach of snapping turtles, northern pike, and other animals that might eat them.
Gradually the young loons grow regular feathers to replace their fluffy down. Unlike the parents, which have black-and-white plumage with a dark head that shimmers iridescent green in sunlight, the young loons are brownish gray with a white belly. By the end of the summer, their down has been replaced by adult feathers and they are able to fly.
As the chicks grow, the parent loons change too. In late summer their black-and-white body feathers fall out and the loons grow a winter coat that looks much like that of their young.
In September the parents begin to gather with other adult loons on large lakes. Around Halloween they leave Minnesota to return to their winter homes in the south.
The chicks stay on their home lake for another month before they gather with other young loons on the large lakes. The extra time helps them grow big enough and strong enough to survive the long trip. They have never been south before, and no adult loons guide them. But instinct guides them to the ocean. They will spend two-and-a-half years there before they return north.
Taking off for flight is hard work for the loons because their bodies are heavy relative to their wing size. They must run along the surface of the water for hundreds of yards, like an airplane rolling down the runway, to get up enough speed to become airborne.
Flying through the air at 55 miles per hour -- as fast as cars on a highway -- the loons migrate to the ocean off the southern or eastern coast of the United States. When they get tired and hungry, they stop to feed and rest at lakes along the way.
SPLASH! After many weeks of migrating, a loon lands in the salty waters of the Atlantic Ocean, more than 1,000 miles from its summer home. Though this ocean habitat is not at all like the pine-scented shores of its Minnesota lake, the loon is just as much at home. It can survive on salty ocean food because glands near each eye secrete extra salt from its body. The adult loon will stay here until spring, filling its belly with fish and growing a fresh set of breeding feathers. Then, nature will call the big bird north once again.