Birds, Eels, and Turtles: Migration and Magnetism
Dept. of Physics and Astronomy, George Mason University
About the LectureThe December 1947 issue of the Journal of Applied Physics published a paper by Henry Yeagley, Department of Physics of Penn State: “A Preliminary Study of a Physical Basis of Bird Navigation”. Fifty years later the Journal of Experimental Biology carried a review by Wolfgang and Roswitha Wiltschko, “Magnetic Orientation in Birds”. What happened in that fifty-year time span? …a study of data on 12,000 Italian racing pigeons and lots of experiments on migrating birds and other animals. Homo Sapiens need compasses, but evolution has provided some species with built-in abilities to navigate using one of the major physical features of our planet.
About the SpeakerEugenie Vorburger Mielczarek is Professor of Physics at George Mason University in Fairfax, Virginia. Her experimental research for twenty years has focused on iron in biological systems. She has been a visiting scientist at the National Institutes of Health and the Hebrew University of Jerusalem and a winner of the Distinguished Faculty Award at George Mason University. She has advised National Public Radio, judged the U. S. Steel-American Institute of Physics prize for science journalism, and chaired the American Institute of Physics' book publication committee. She belongs to the East Coast Iron Club, a group of about forty scientists who study iron in biological systems. She is the primary editor of Key Papers in Biological Physics. Ms. Mielczarek received her B. S. Degree in physics from Queen's College, Flushing, N.Y., and her masters and Ph.D. degrees from Catholic University, Washington, DC.
President Agger called the 2087th meeting to order at 8:20 p.m. on March 6, 1998. The Recording Secretary read the minutes of the 2086th meeting and they were approved. The speaker for the 2087th meeting was Eugenie Mielczarek, Professor of Physics, at the George Mason University. The title of her talk was, “Birds, Eels and Turtles: Migration and Magnetism.” Millions of creatures migrate to spawn, reproduce, feed, etc. including salmon, whales, eels, turtles and birds. Many species navigate thousands of miles to the exactly same place every year. Further, many do it only one time and then die. For years this migratory navigation, against adverse weather and physical conditions, was the considered an incredible phenomenon that puzzled biologists. More than fifty years ago, in 1947, one Professor Henry Yeagley of Penn State University published a paper entitled, “A Preliminary Study of a Physical Basis of Bird Navigation.” It had long been noted that Homing pigeons always seemed to get lost around the magnetic anomalies. It was also observed that Homing pigeons always got lost during periods of high sun spot activity that upset the earth's magnetic field. This was particularly annoying during the sun spot activity periods of 1957 and 1976 when a large number of Italian racing pigeons didn't show up at the finish line. Finally, in the 1960's, experimental studies were initiated to assess the navigational tools used by many migrating birds. Migratory birds were studied because they're small and manageable. It wasn't until the 1980's that it was accepted that birds were using the earth's magnetic field as their navigational tool. However, the birds weren't using the traditional “which way is north” magnetic field of the earth. They were using the earth's magnetic dip angle as the actual tool used to steer them on their way. The dip angle is the inclination of the earth's magnetic field to the surface of the earth. It is the phenomenon where the magnetic lines of flux point out of the earth at the South Pole and back into the earth at the North Pole. Consequently, they lay flat and parallel to the ground at the equator. Scientists have detected tiny crystals of magnetite along the olfactory tract in the brains of some birds. Magnetic particles have also been found in the noses of migratory trout and salmon. Further, it was found that Homing pigeons with small iron magnetic bars taped to there head always got lost on cloudy days. Whereas Homing pigeons with small brass bars taped to their heads always managed to get home. Similar studies using pigeons with frosted “contact lenses” almost got home but they needed visual cues to finish the trip. By blending the disciplines of physics, chemistry and biology, Ms. Mielczarek debunked other parameters as cues for birds to navigate along their migratory pathways. Although birds do orient to stars on clear nights, they also navigate quire well on cloudy nights. Further, proposed cues using pulsars and quasars and other forms of cosmic radiation won't work if for no other reason than they require meter-wide dishes as antennas. Ms. Mielczarek then closed her presentation and kindly answered question from the floor. President Agger thereupon thanked Ms. Mielczarek for the society, announced the next meeting and made the usual parking announcement. She then adjourned the 2087th meeting at 9:44 p.m. Attendance: 54 Temperature: 8.5°C Weather: clear Respectfully submitted, Bill Spargo Recording Secretary