Common loon parents take turns feeding their young chicks. At first the adults hold the fish until the chick grasps it, but soon the parents will be dropping the live food they catch several inches away from their chicks, in an attempt to teach their young to catch their own food. (Photos by Mary Holland)

For the first two weeks of their life, common loon chicks can be seen riding on their parents’ backs. Because they aren’t able to regulate their own body temperature yet, the chicks need the warmth of their parent’s body and crawl under their wings when they are cool.

If their waterside nest has not been flooded, predators such as raccoons have not raided their nest, and humans haven't disturbed them and driven them off their nest, the eggs of the common loon generally hatch in July. The two parents take turns the month before incubating their two eggs. Often the chicks announce their impending entrance into the world with audible peeps issued from within the egg as many as four days before hatching. Once they've hatched, and their sooty, black coat of down has dried, the chicks are off and running, straight into the water.

The parents actually coax the chicks off the nest by calling them softly from the water. The chicks can immediately swim, and even dive on their first day. By the second day, they will be chasing minnows (but rarely catching them). The parents must carry, feed, and defend their chicks for several weeks. During the first week or two of their life, loon chicks are not able to regulate their body heat very well, and the parents must provide the warmth necessary for the chicks' survival. They do so by brooding them on their backs, underneath their wings, instead of in the nest, as most birds do. While in the water, the chicks scramble up the sides of their parents and snuggle in under their raised wings. When the adult's wings are lowered, you would never know there was anything under them. On warm, sunny days the chicks often emerge from under their parents' wings and ride around on their backs, enjoying the view. Occasionally they are fed by one parent while they ride around on the back of the other parent.

Soon after their chicks enter the water, the adult loons move them to a nursery area (the chicks usually follow their parents, swimming under their own power). Typically, the nursery is a shallow cove or back bay that is protected from strong winds and waves and has an abundance of small fish. For the next two weeks, or, if conditions permit, even longer, they will remain here under the watchful eyes of their parents, who guard against predators such as bald eagles and snapping turtles.

Common loon parents feed their young for the first three months of their lives, although increasingly less and less as the chicks become more and more independent. During the first two weeks, the adult swims up to its chicks holding a fish crosswise in its bill. This exerts pressure on the fish in a way that partially paralyzes it, making it easier for the chick to grasp the fish. Once the chick has hold of it, it shifts the fish in its beak so that it will go down its throat head first. During the first week or two, the chicks stay put with their mother, while their father provides much of the food, which consists of aquatic insects, small fish, and crayfish (by the end of the first month the parents take turns chick-sitting and fishing). By the third week chicks start to follow the adults while they fish, and approach them when a meal is caught. By the fourth week, the adults tend to drop fish that they've caught a few inches away from the chicks, making their young dive after and retrieve the fish, thus teaching them how to catch their own food. By the end of eight weeks, the chicks are supplying at least half of their own food; by the end of 11 weeks they are catching 90 to 100 percent of their food. As the chicks grow older, they are left alone more and more frequently, and for longer periods of time.

Just as their feeding routine changes with age, so does the chicks' plumage. Common loons are unusual in that their young have two successive coats of down. This makes it possible to roughly tell a chick's age by its appearance. The original black down is pushed out by a secondary brownish-gray down when the chicks are between 10 days and two weeks old. This second coat of down is, in turn, replaced by a sleek juvenal plumage, which is complete by the age of 10 or 11 weeks, providing the chicks with feathers that permit flight.

Loon parents provide their offspring with warmth, food, protection, and survival skills that will see them through the next 25 or 30 years. This year's chicks will migrate to the East Coast this fall, where they will remain for the next three years. Then they will return, to continue the cycle and provide us with their incomparable sight and sound. (Common loons can be found at Quabbin and Wachusett reservoirs.)

Mary Holland blogs about natural history at www.naturallycuriouswithmaryholland.wordpress.com.