Like the migratory loon that is the subject of his new book, Bill Sullivan spent years traveling between New Hampshire and his native Rhode Island.

The loons nest in the north and fly south each fall, wintering off the Westerly shore. Sullivan headed to New Hampshire each September, to teach English at Keene State College, and traveled to Westerly for summer vacations. But it was in New Hampshire, during camping trips to the White Mountains, that he first encountered the sharp-billed bird.

After retiring to Westerly in 1998, he was surprised to hear the loon’s cry off shore during winter walks in Weekapaug.

“I did get to love them in New Hampshire,” he recalled last week when asked to discuss the bird’s appeal. “It’s elusive. It’s very beautiful. So in sight and sound, it’s very attractive.”

Sullivan’s poetry and essays about the loon have been collected in a new book, “Loon Lore: In Poetry and Prose,” published by Grove Street Books. The collection features illustrations by Leslie Tryon, Sullivan’s cousin and a children’s book author and illustrator.

Sullivan and Tryon will discuss “Loon Lore” Tuesday at 6 p.m. at Avondale Arts, 95 Watch Hill Road, Westerly. The event, sponsored by Bank Square Books, will include readings, images and a unique soundtrack — the call of the loon.

Its unique cry is haunting, almost human-like. In his poem “Henry and the Loon,” about Henry David Thoreau’s view of the bird, Sullivan describes it “laughing like/an ancient trickster mocking a mortal’s quest/as he swam behind heaven’s blinding mist.”

The book’s seven poems were originally collected by the Origami Poets, a local group that distributes free poetry collections folded in two-inch-wide booklets. They explore the bird through history, myth and science, but after the poems were completed, Sullivan found he had more to say.

Prose “gave me a chance to talk about some larger things,” he said. “You can begin to talk about fossil fuels. Preservation of land. Wilderness attitudes.”

In the essays, Sullivan paints a compelling picture of how human activity — including global warming, fossil fuel use and development — has endangered the loon. The North Cape oil spill off South Kingstown, R.I., in 1996 and a 2003 spill in Buzzard’s Bay in Massachusetts killed a total of 600 loons.

In New Hampshire, where the loons nest, insecticides, heavy metals and mercury have been blamed for a drop in nesting pairs. In particular, lead fishing sinkers can be ingested by loons, who mistake them for pebbles they consume to help digest food. Lead was responsible for more than half of loon fatalities in that state from 1992 to 2008, according to the book.

Whether people care about preserving the loon depends on their attitudes toward nature. And Americans, Sullivan and Tryon agree, are full of contradictions in this regard.

“We have this kind of strange dichotomy as to how we approach land values,” Sullivan said. “One is exploitation — get as much out as quick as you can, and be damned with the results. And the other is wilderness in its own right has great value.”

Sullivan, of course, takes the latter view. Learning about nature, and the loon in particular, helps humans appreciate the scale of time, he believes. The birds have existed for at least 35 million years, surviving the glacial ice sheets that retreated from Rhode Island 18,000 years ago. One of the most poignant illustrations in “Loon Lore” is of a loon swimming alone past massive icebergs.

Tryon has written and illustrated 10 children’s books and illustrated as many more. She brought to this project a deep respect for the writer’s process. “Words first” is how she puts it.

“I have such great respect for Bill’s poetry, that for me it was easy to keep myself separate, to come after,” she said.

She read everything she could find on the loon and studied photographs, struck by the bold contrast of its colors: black head, black and white feathers, and red eyes.

But it was not until the book was completed that she happened to see a stuffed loon at the Peabody Essex Museum in Salem, Mass., and she could not believe how large and ungainly it looked.

“When I saw its size, I did not particularly think this bird had the capability of being graceful,” she said, noting the specimen stood about three feet high.

“You hardly ever see them out of water,” Sullivan added.

In addition to her publishing career, Tryon teaches tap dance and has choreographed high school, semi-professional and professional musicals. “That informs illustration,” she said, “because you’re used to working with the proscenium, and that becomes the two-page spread.”

The cousins, who sometimes finish each other’s sentences, spent childhood summers together in Rhode Island, although Tryon was raised in California. Today both live in Westerly.

At his home north of Shore Road, Sullivan rises early, writing at the breakfast table. He then walks to Weekapaug, where he might mull over ideas or be inspired by the sights and sounds of the sea, which include the loons frolicking off shore.

He hopes “Loon Lore” might inspire others to appreciate and defend the bird of the haunting cry.

“Hopefully people will see it as sort of a way to get close to the world, maybe playing a role in preserving it,” he said. “If it were helpful in that way that would be great.”

The author is a former student of Bill Sullivan and wrote a blurb for the back cover of Loon Lore.

IF YOU GO

What: A talk on “Loon Lore” by author William Sullivan and illustrator Leslie Tryon

Where: Avondale Arts, 95 Watch Hill Road, Westerly

When: Tuesday, Jan. 12, at 6 p.m.