By Susan Milius
A survey of 19 species of sandpipers is changing scientists’ ideas about why the birds switch from one glandular wax for preening their feathers to a different one.
Ornithologists had long presumed that each bird species makes only one kind of wax. Its purpose, researchers have speculated, is to slow down feather wear and make the feathers flexible and water resistant.
Wax switching came to scientific attention in 1999, when Theunis Piersma of the University of Groningen in the Netherlands and his colleagues described an abrupt seasonal shift in wax composition among sandpipers called red knots (Calidris canutus). As breeding season approached, the birds stopped producing a wax made of molecules known as monoesters and secreted a more viscous diester wax. At first, the researchers proposed that the birds were putting on a special make-up for their dates.