The researchers published their findings May 23, 2005, in the early online edition of the Proceedings of the National Academy of Sciences. The collaboration was led by Henrik Mouritsen of the University of Oldenberg in Germany and Erich Jarvis of the Duke University Medical Center. Other co-authors were Gesa Feenders and Miriam Liedvogel in Mouritsen's laboratory and Kazuhiro Wada in Jarvis's laboratory. The research was supported by the VolkswagenStiftung to Mouritsen and the National Science Foundation's Waterman Award to Jarvis.
To migrate successfully over thousands of miles at night, night-migratory birds need to see where they fly, as well as navigate by stars and the earth's magnetic field. Surprisingly, Jarvis said, recent scientific evidence has suggested that birds have specialized molecules in their visual system that translate magnetic compass information into visual patterns. Thus, , the researchers hypothesized that night migratory birds would need a specialized night-vision brain area.
"There was no evidence of such a specialized region in night migratory birds before we began this research," Jarvis said.
In their study, the researchers compared two species of night-migratory songbirds -- garden warblers and European robins -- with two non-migratory songbirds -- zebra finches and canaries.
Using a transparent cylindrical cage in Mouritsen's laboratory, they first accustomed the birds to the illumination equivalent of moonlight. They waited until the birds were sitting quietly to eliminate brain activity from movement. The researchers then quickly preserved the birds' brains, and in Jarvis's laboratory analyzed the
Source:Duke University Medical Center