On a still, late summer night, a soft, deep, rapidly repeated “co-co-co-co” sometimes betrays the presence of one of Canada’s most surreptitious birds. By day, the mysterious black-billed cuckoo—about the size of a blue jay, but much sleeker—keeps silently out of sight. When it’s not hunched stalk still, it’s slinking slowly through dense, tangled forest edges and understory, or shrub thickets and thorn trees.
Cuckoos are connoisseurs of caterpillars that are too hairy, too spiny, or too toxic for most other birds. Ingested bristles stick into the long-tailed bird’s soft, regenerative gizzard lining, eventually coating the lining like fur until it detaches and the cuckoo coughs up the whole mass as a pellet.
Returning late in the spring from South America, cuckoos wander across Canada, east of the Rockies, for…
