In another article an Atlantic tern which migrates from Nova Scotia to the North shore of South America were tested in a different manner. They were encased in a sphere which was painted black. Inorder to test the thesis, the scientists changed the day night cycle to get the bird on a standard time. When migration is about to begin the bird's genetalia shrink. Thus there is less body weight for the long migration. The sphere that housed the birds had minute holes which were made so that the Northern Hemisphere Celestial Sphere was portrayed. The inside of the shpere was covered with carbon paper and as the migration began the birds would try to launch themselves southward. From the bird tracks in the sphere the scientists concluded that these birds also performed a rudimentary form of celestial navigation.
Ain't it amazin'?
We already knew that birds could read Earth's manetic lines, and celestial navigation would be important as birds migrate at night. That birds see magnetic lines and navigate by stars is new.
By the way, UNC/Chapel Hill, is active in some elegant studies to determine just how closely birds evolved from dinosaurs. I don't agree with their findings, but their bird limb ontogony observations were very nicely done. I agree with this observer: http://www.dinosauria.com/jdp/archie/paulfed.html
They return north the same way, using the air currents.
It might be possible to train a bird to respond to radio signals. Someone with lots of time on their hands could put out bird food randomly along with various strong radio signals and see who shows up. Hmmm, I'll change my voter registration to Democrat, apply for a government grant and take a really long vacation. I have to work global warming into the grant request somehow.