To discover where prothonotary warblers spend their winters, Beidler staff devised an ingenious system. Several birds, weighing about half an ounce, have been fitted with tiny backpacks that record information about where they go. The devices don’t transmit coordinates, they would be too heavy. This system is dependent on having some of the birds, with their site fidelity, successfully making the trip south and returning to the place of their birth. Then they’re trapped, the backpacks removed, and information retrieved. The birds use mangrove swamps in Central and South America as their winter resting grounds, and destruction of those areas is a grave threat to their existence. With Project Protho, Audubon and other groups study migration patterns in an attempt to protect these birds not only in their North American breeding grounds but in their winter habitat as well.