Effects of low-level RF fields reveal complex pattern of magnetic input to the avian magnetic compass

Abstract

Overview

The avian magnetic compass can be disrupted by weak narrow-band and broadband radio-frequency (RF) fields in the lower MHz range. This disruption may involve changes that make the magnetic pattern unrecognizable to the birds.

Findings

• Zebra finches trained in a 4-arm maze to orient relative to the magnetic field are disoriented in the presence of low-level (~ 10 nT) Larmor-frequency RF fields.
• If trained under the RF condition, zebra finches can orient correctly, indicating alteration rather than elimination of magnetic input.
• Higher intensity Larmor-frequency RF fields, regardless of the presence of harmonics, dramatically alter the compass response.
• Exposure to broadband RF fields in both training and testing phases leads to the elimination of magnetic compass information.

Conclusion

The study delineates how exposure to different types and intensities of RF fields can variably affect bird's perception of magnetic fields, greatly influenced by their familiarity with the RF-generated pattern.