I used to get such joy thinking about loons and their interpersonal relationships. Here’s what I cherished: Loons choose a partner, have chickies, and then stay together for life. None of this divorce stuff for them. And if a high-ranking loon has an intern, you can bet he won’t have sex with her. Ah, the common loon — so uncommon really.

So it came as a shock when I read recently in “Just Loons: A Wildlife Watchers’ Guide,” a new book by Alan Hutchins and photographer Bill Silliker Jr., that it is now believed loons don’t always mate for life. Sometimes, they mate for just one summer.

I am seriously depressed by this news. Anyone can mate for a summer. It takes a real loon to mate for a lifetime. Even Dr. Laura knows that.

But please somebody tell me: Will monogamy ever find a place among civilized animals again?

Probably not.

At the risk of rationalizing behavior I cannot support, I have to say that, besides this recent revelation about the promiscuity of loons, Hutchins and Silliker deliver a profile of an otherwise admirable species. Let’s just say if you’re not into marriage, but you would like to have a meaningful relationship for a limited amount of time, the loon’s life may be for you.

First of all, it involves summering in some of the country’s most exquisite lakes which are essentially claimed by squatter’s rights. If your great-great-great-grandfather loon summered on Echo Lake, then it’s probably still in the family. In the winter, you move to the coast and eat crabs. As an old crab lover myself, I can dig that.

Now for some structural pluses. You have thrusters that compare to the most powerful of submarines, you have 360-degree vision, and, since you’ve been around 20 million years, you’re a model of durability. You can fly, you can swim, you can sing like Billie Holiday.

What you don’t do so well is walk on land. Think about it: Ever seen the front legs of a loon? Of course not. That’s because they don’t exist. Loons spend 99 percent of their time in the water, which, in these days of loon liberality, presumably means chasing female loons.

Silliker’s photos show loons walking, and it’s a pretty sad sight — butt in the air, front dragging on the ground. Embarrassing, really. You can nearly hear the thud of a loon’s body as it takes to land, which is does only for nesting purposes, thank goodness.

That brings us to the part of loonhood that retains its fairy book quality. This is the part I still love about loons. Both parents help incubate the eggs, and then both parents help train the chicks to eat, fly and communicate. The dad doesn’t go off to Mexico for a work assignment, and the mom doesn’t run off frolicking with her loonette pals from high school. No, Mom and Dad stay together, fighting danger, staking their ground, getting groceries and redecorating the nest.

Although Hutchins and Silliker would never support my total anthropomorphism of loons, I have to say I find the whole thing rather romantic. Except for the infidelities, of course. But the rest of loon love: pure domestic bliss. Consider this: When loon couples are not using their wailing voice to warn chicks about threatening predators, they use it to whisper sweet nothings to each other.

So you can see why I am upset to learn that loons, once the archetypes of lifelong love, are now believed to be more common than I orginally thought.

Of course, none of this is the point of this “Just Loon,” which, in my current state of disappointment, I think should be called “UNjust Loon.” Hutchins and Silliker are much more high-minded than I. They don’t judge loons. They illuminate them — both by sharing their knowledge of the loon habitat and by depicting the loon in every aspect of that habitat. (A calming note for the terrifically paranoid: Don’t be emotionally agitated if you can’t find a loon in every photograph. It’s perfectly OK to say (as I did), “Hey, that’s not a loon; that’s a moose!”)

The best part of this book is that it is easy to read. That’s not unusual for a coffee-table-book format. But here’s the unusual part: I read every word and learned a lot about the life and times of the common loon. Who’s more common than I thought.