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The team planned to tag humpbacks with custom-built instruments containing pressure sensors, accelerometers, magnetic compasses and hydrophones that record their underwater behavior, along with a radio transmitter to enable tracking.

In response to Alexander: Tracking devices usually employ frequencies well beyond 100 megahertz, which are very unlikely to affect the birds' magnetic compass.

Last, even though songbirds fly at night under the dim light of the stars, their magnetic compass is light-dependent, hinting at a link between vision and magnetic sensing.

The magnetic compass — used in navigation for hundreds of years — is a tool that helps you find your way.

Just as you might reach for a magnetic compass to find which way is north or south, birds are thought to have an in-built "living compass".