The common loon is an uncommon bird, one of five loon species sharing a long history, and believed to be most closely related to — wait for it — penguins.

The other four loons are Pacific, Arctic, red-throated and yellow-billed.

Red-throated and Pacific loons are regularly seen here as migrants, most easily found on Lake Superior, off Park Point in Duluth. The yellow-billed loon is accidental here, with six sight records.

The common loon, though, is our magical bird, a favorite, perhaps most particularly for its wailing, yodeling voice.

It is seen throughout the state in spring migration, nesting in the northern two-thirds of the state.

A new book has been published about this bird. "Loon Lessons: Uncommon Encounters With the Great Northern Diver," by James D. Paruk. It will be released on June 29 by the University of Minnesota Press ($29.95). Great northern diver is the bird's name in its Eurasian distribution.

Paruk has studied loons in several states and Canada for almost 30 years. He is a professor of biology, and is associated with various loon conservation programs. He has written a complete and entertaining account of the bird's history and biology.

Paruk says it appears that loons and penguins shared a common ancestor 50 million to 55 million years ago, making them one of the oldest living lineages of birds.

Skeletons of all five loon species, as they assumed individual characteristics, date from the Pleistocene, more than 2 million years ago.

Loon species come small, medium and large. Red-throated are smallest, common and yellow-billed the largest. Common loons weigh from seven to a solid 12 pounds. A bald eagle is 25% larger but weighs about the same.

A bigger loon with a larger bill, common loons can dive deeper, stay submerged longer, eat larger and more varied species of fish, and can eat larger crustaceans. (Average submerged time is about 30 seconds.)

There are reasons for the loon's characteristic black and white plumage. Black feathers contain more melanin and keratin (the protein in our fingernails and toenails), which makes them stronger than lighter colored feathers.

Loon feathers are stiff, compressing the loon's body when it dives, easing passage through the water. The loon's teardrop shape does the same.

The black and white pattern is easily visible from the air, offering no camouflage protection from predators like eagles. Instead, Paruk believes, loons, solitary birds, want to be seen, to tell other loons that this lake is occupied: Don't stop here.

On the other hand, the white belly, a feature of almost all diving bird species, makes the loon difficult to see from below. Common loons winter on saltwater where predation by fish is possible.

Loon legs are another adaptation for diving and hunting underwater. They are set far back on the body, making the birds excellent swimmers but awkward on land.

Paruk believes the Scandinavian words lom or lumme, meaning clumsy, are the source for the name loon.

Loons swim like you paddle a canoe: twisting the blade (the foot) on the return stroke to minimize drag.

The skull of a common loon is thick and heavy for a bird, and some of its bones are solid, uncommon in birds. This adds weight, which makes it easier for the bird to dive.

Ducks will burst off the water in flight instantly to escape disturbance. Loons are too heavy for that. They also have a very shallow keel — breast bone — again to reduce underwater drag. Flight feathers are attached to that bone, so the loon swaps stronger wings for swimming skills.

Loons splash across the water to gain the speed needed for flight. It's what Paruk calls an ecological trade-off; loons can't be good both at fishing and fast off the water.

There is so much more in this 217-page illustrated book. Titles of all research papers used in gathering information for the book are included at the end of each chapter, an idea of convenience. A simple Google Scholar search makes them available to you.

Lifelong birder Jim Williams can be reached at