By Nsikan Akpan
For more on small drones inspired by birds and other flying animals, see SN’s feature “Flying animals can teach drones a thing or two.”
Last summer, biophysicist Douglas Warrick spent eight hours each day patiently sitting on the fence of an Oregon cattle farm. Pointing an alienlike metal wand toward a field, he waited. The rod was a special antenna designed to listen for very small radiotags. Earlier that week, Warrick and his team from Oregon State University had glued these tiny trackers, weighing less than a third of a gram, to 120 barn swallows (Hirundo rustica).