The first utilizes olfaction to detect odors from volatile hydrocarbon gases in the atmosphere. In recent years, two environmental cues have been proposed as bases of a navigational map. Birds must have a map stashed somewhere in their brain that shows gradients of an environmental cue (or cues) as a spatial network that can be interpreted and followed. For example, the odor of an atmospheric gas might be greater at one place than another, or the intensity of the magnetic field might be stronger here, weaker there. To function as a map, an environmental cue must be present in a gradient form, so birds can differentiate between levels or amounts in different areas. But science has never agreed on an acceptable navigational map.

A compass can guide birds to a region, but not to particular sites within it.

Photo by guentermanaus/Shutterstockīirds have internal compasses that can determine directions from the sun’s position during the day, star patterns at night, and Earth’s magnetic field. EXPERT NAVIGATORS: Homing pigeons have flown as far as 1,000 miles in competitions.