Bat
Microbats make use of magnetoreception, in that they have a high sensitivity to the Earth's magnetic field, as birds do. Microbats use a polarity-based compass, meaning that they differentiate north from south, unlike birds, which use the strength of the magnetic field to differentiate latitudes, which may be used in long-distance travel. The mechanism is unknown but may involve magnetite particles.
Amelia Earhart
It is unknown whether the model 20B receiver had a beat frequency oscillator that would enable the detection of continuous wave transmissions such as Morse code and radiolocation beacons. Neither Earhart nor Noonan were capable of using Morse code. They relied on voice communications. Manning, who was on the first world flight attempt but not the second, was skilled at Morse and had acquired an FCC aircraft radiotelegraph license for 15 words per minute in March 1937, just prior to the start of the first flight.