A silent die-off at sea: bird flu reaches Costa Mar's seabird colonies

The boat cuts through the water at dawn, and what should be a riot of sound is quiet. Rodrigo Ávila, a marine biologist with the Costa Mar Reef Monitoring Network, stands at the bow of the research vessel Pelícano and listens to the absence. The island ahead—Cayo Blanco, a limestone outcrop thirty kilometres off Puerto Azul—holds a breeding colony of magnificent frigatebirds that has been counted, measured, and photographed by the Network for twenty-three years. On this June morning, the colony is half its usual size, and the birds that remain are lethargic, their movements slow and uncoordinated.

Ávila and his team collected tissue samples from seven dead birds over three days last week. The National Veterinary Institute in Puerto Azul confirmed H5N1 avian influenza in all of them. It is the first documented case of the virus in Costa Mar's marine bird populations, and it has arrived at a moment when the reef ecosystem is already stressed by warming water and shifting fish populations.

The discovery raises questions that no one in the region is yet prepared to answer: How far will the virus spread through the seabird colonies? What happens to the reef food web when the predators that keep it in balance begin to disappear? And what obligations do Costa Mar's conservation authorities have to intervene in a natural disease process, especially when intervention itself carries ecological risk?