“Unraveling the Mystery of Avian Navigation Using Propagation Modeling of Atmospheric Infrasound”
Prof. Jon Hagstrum (U.S. Geological Survey)
Friday May 22, 2015 — Marine Science Institute Auditorium, Room 1302, UCSB — 2 pm–3:30 pm
(Followed by coffee and refreshments)
Abstract. Birds navigate over hundreds to thousands of km during migration, foraging, and homing with pinpoint accuracy, and this phenomenal ability is thought to involve a two-step process. Solar, magnetic, and stellar compasses (the “compass” step) orient avian flight, but how birds first determine their location in order to select the direction to their destination (the “map” step) has remained an enduring mystery. Homing pigeons, the model species, have a greater number of senses than humans and can detect small changes in barometric pressure (<1 mbar) and in the weak geomagnetic field (~10 nT); they also possibly have a built-in Pitot-static airspeed system. Avian navigational “maps” based on gradients in the geomagnetic field and in atmospheric odors have been proposed, but have significant theoretical difficulties and cannot explain common observations from pigeon release experiments. One avian sense, however, that has received relatively little attention in terms of a navigational sense is hearing. Laboratory experiments have demonstrated that pigeons can hear infrasound down to ~0.05 Hz, and such signals can travel relatively undiminished for thousands of km in the atmosphere. Acoustic propagation modeling indicates that pigeons are disoriented in acoustic “shadow” zones relative to their home loft, and that intervening topography and varying wind and temperature fields produce acoustic effects that can be related to pigeon behavior during experimental releases. In addition, seasonal changes in atmospheric noise levels, generated globally by interacting ocean waves, likely cause seasonal changes in homing performance.
Bio. Jon Hagstrum has worked as a research geophysicist with the U.S. Geological Survey since 1979. He holds a Ph.D. from Stanford University, an M.S. from the University of Michigan, and a B.A. from Cornell University. His body of work lies primarily within the fields of paleomagnetism, geomagnetism, structural geology, and plate tectonics. More recently his research topics have included the geophysical underpinnings of animal navigation, the geological effects of large-body oceanic impacts during the Phanerozoic, and regional extinction events in the Late Pleistocene.
This lecture is presented by the SYSTEMICS PUBLIC PROGRAM led by Prof. Marko Peljhan and the UCIRA INTEGRATIVE METHODOLOGIES series, in collaboration with the UCSB Center for Spatial Studies and the Media Arts and Technology program.