Nature unveils the unseen world of songbirds:
They injected one tracer into the part of the forebrain known to be the only active area when birds orient themselves (known as Cluster N), and a different tracer into the retina.
After a bird experienced a desire to migrate, both tracers ended up in the same place, the researchers report in the Public Library of Science One1 — a part of the thalamus responsible for vision.
This anatomical link strongly supports the notion that the birds probably experience magnetic fields as a visual sensation, say the researchers.
They migrate so precisely because they can see things we can’t – magnetic fields. (Somebody tell Stephin Merritt!)
There’s more on this at NPR.org.