Extended Data Fig. 8: The magnetic conditions used in the electrophysiological (b) and behavioural rigs (a,c,d).

a,b, The Helmholtz coil system was used to compensate the local geomagnetic field and create a “nulled” or near-zero magnetic field (NZMF) within the two experimental rigs. The typical variation of the magnetic field strength, shown as nanotesla (nT) over time (s), for the duration of a typical behavioural experiment (300 s). This measurement was made at the position of the moth (position 0 in d). The three-component vector (X, Y, Z: red, green and purple lines respectively) of the field was measured 6 times over 300 s to obtain X, Y and Z traces. These six traces were averaged to give the mean magnetic field strength for each component (X, Y and Z) and the standard deviation (shaded areas around the mean). c,d, To control that the central area of the arena (where tethered moths flew) had a nulled magnetic field, the magnetometer probe was positioned at the arena centre (position 0 in c) and moved outwards in 1 cm steps along 4 directions (coloured arrows in d) relative to geographic North (gN) and the strengths of the X, Y, and Z field components were measured at each position. These field strengths were less than 100 nT a radius of 4 cm from the coil centre (dashed yellow line and circle in c and d) in all four directions (bar colours in c correspond to direction colours in d). Since the wingspan radius of a Bogong moth is about 2.5 cm (dashed brown line and circle in c and d), this indicates that the entire moth experienced a magnetic field strength substantially less than 100 nT, effectively a “nulled field” (which can be compared to the external local magnetic field strength of around 58,500 nT).