The Role of Magnetic Stimuli in Animals In as early in the year 1855 Minddendorf proposed the idea of broad front, one-direction migration also suggested a means of orientation, that birds were capable of detecting the magnetic poles and of maintaining their bearing therefrom. Since then many similar ideas have continued to pop up at random intervals (Carthy 56). An immediate difficulty is the lack of any structure or tissue that could possibly react to the magnetic field. In the year 1948, the discovery of certain forces were indeed produced by placing ‘non-magnetic’ material in a magnetic field, however they were far too minute to merit any serious consideration (Carthy 59). Some reports speak of heightened locomotor activity and heartbeat, when in close proximity to increased magnetic fields; a fact which might mean that a kinesis-based magnetism is a possibility. A study was done in which magnets were attached to birds and released in sunny (or starry) conditions have repeatedly been shown to have no effect on orientation (Dorst 24). However recently it has been shown that pigeons repeatedly released under conditions of heavy overcast (in areas where the recognition of landmarks could not rigorously excluded) have an orientation which is disturbed by magnets. Most workers with caged birds have failed to find any tracer of orientation in a planetarium with all the stars blocked off or in any closed room (32). This phenomenon definitely shows evidence that some if not all birds use celestial bodies. One group studying magnetic orientation in birds has consistently claimed to the contrary. Their accumulated data does seem to show some directional tendencies but the scatter distribution is so wide that their significance could be said to be more statistical than biological. There are suggestions that there may be at least a north/south klino- or tropptaxis to the magnetic field. It must be remembered that no-one...
