A father whose mind is failing, a planet in distress: Author Susan Cerulean illuminates the links between them in her new book, I Have Been Assigned the Single Bird: A Daughter’s Memoir .Cerulean is a writer, naturalist and activist based in Tallahassee. Her other books include Coming to Pass: Florida’s Coastal Islands in a Gulf of Change and Tracking Desire: A Journey After Swallow-tailed Kites .In I Have Been Assigned the Single Bird , Cerulean writes with compassion and insight about her beloved father’s decline due to Alzheimer’s disease. Over five years, she and her family care for him as dementia robs him, little by little, of self.During those years, Cerulean volunteers as a steward of wild shorebirds on a tiny island just south of the Apalachicola bridge, paddling out in her kayak to observe and protect nesting birds, including least terns and American oystercatchers. That experience brings her solace, but it also brings into focus a kind of “cultural dementia” that threatens the global environment.In her memoir, Cerulean writes elegantly of the grief and grace those experiences brought her.Here is an excerpt from the prologue of I Have Been Assigned the Single Bird :One afternoon, during the second September of my father’s stay in the nursing home, I stood near his bed and pressed my forehead against the window. Through the glass, I could hear the muffled calls of cardinals and red-eyed vireos. I did not open the windows, for the late summer air steamed like a thick hot pudding.When we first moved Dad into that room, the emerald green light filtering through the windows had reminded me of swimming underwater in a warm river. It wasn’t really so bad, like you might fear kudzu-mediated sunlight could be. But as time passed, I noticed that many of the tall pines around the nursing home were dying under the weight of the vines swarming their living canopies. I saw that those smothering lianas were like the tangles and plaques in my father’s brain, how both kudzu and Alzheimer’s replace a vibrant living place — a brain once full of inborn competence and memories of long-gone houses and long-grown children — dissolve those things in super-slow motion, replacing them with loss. Dad’s drugs, the Namenda and the Aricept, were like winter frost in the forest. For a time, they would keep the plaques in his brain at bay. Link by link, the invasive vines weighted that scaffold of mature trees with blankets of biomass. I could still make out the biggest magnolia setting its red fall fruit, but I didn’t know if it would survive until freezing December nights slashed the tough kudzu back to its knees. I Have Been Assigned the Single Bird: A Daughter’s Memoir By Susan CeruleanUniversity of Georgia Press, 176 pages, $24.95 Times Virtual Festival of Reading Starting Nov. 12, watch an interview with Susan Cerulean at festivalofreading.com.