Mite life

Natural History, Feb, 2002 by Kirsten L. Weir

Around the world, birds harbor symbiotic mites of the suborder Astigmata. For the most part, the so-called feather mites live a quiet life, hanging out on the surface of bird feathers, feeding off oil and fungi. Once a year, though, when the birds molt, the tiny arthropods face life-or-death options. A mite that's hitched itself to a falling feather can kiss its home good-bye.

Do mites try to avoid being discarded along with molted feathers? To find out, biologists Roger Jovani and David Serrano, of the Estacion Biotbgica de Dohana in Seville, Spain, studied sixty-three songbirds from thirteen species. Because these songbirds replace wing feathers in the same sequence year after year, the researchers could easily determine which feathers were ready to molt. They discovered that most mites wouldn't be caught dead on the feather that was next in line to fall -- or the one after that. This held true especially for the primary, or outermost, feathers.

How do mites sense imminent feather fallout? One possibility is that they perceive changes in air currents flowing through gaps created when nearby feathers drop. Another possibility, favored by Jovani and Serrano, is that the mites are able to detect the vibrations in feathers that are loosening. Apparently for feather mites, choosing a home is all about "location, location, location." ("Feather Mites [Astigmata] Avoid Moulting Wing Feathers of Passerine Birds," Animal Behaviour 62:4, 2001)