As dawn breaks over the southern fringe of the Great Barrier Reef, a deafening chorus rises from the dense canopy of Heron Island. Thousands of black noddies ( Anous minutus ) stir from their roosts, their dark silhouettes contrasting sharply against the pale limbs of the Pisonia grandis trees. These highly specialized seabirds, characterized by their charcoal plumage and brilliant white caps, are the architects of a remarkable biological bridge. They link the deep, open waters of the coral reef with the fragile, terrestrial island ecosystems that dot the Pacific. For centuries, these coral cays have remained lush oases amid nutrient-poor tropical waters, sustained entirely by the cyclical migrations of seabirds. But recent ornithological surveys and marine-ecological studies have uncovered a disturbing vulnerability in this ancient relationship. The survival of the black noddy—and by extension, the entire terrestrial ec...