Sun Sets Songbirds' Compass.

Songbirds can migrate for thousands of kilometers at night and in poor weather yet still end up in the right place. Now, in a logistical tour-de-force, three researchers have revealed how the birds get their bearings before takeoff each night: They set their course according to a magnetic compass they calibrate at sunset. By watching which direction the birds try to hop out, researchers try to discern which sense the birds rely on most. The researchers followed the birds as they flew through the night, tracking them with a meter-tall antenna mounted on top of a battered 1982 Oldsmobile. Control birds flew northerly, but those that had been in the altered magnetic field flew westward for the entire night.