Abstract
There is a consensus that birds detect the earth’s magnetic field and use some of its features for orientation and homing purposes. Since the late 1960s, when the first solid behavioral evidence of magnetoreception was obtained, much research has been devoted to describing the ethological aspects of this behavior. The neurophysiological basis of magnetoreception has been much less studied, although a frequently cited 1986 report described a high prevalence (70 %) of magneto-sensitive neurons in the pigeon optic tectum with high signal-to-noise ratios (Semm and Demaine, J Comp Physiol A 159:619–625, 1986). Here, we repeated these neurophysiological experiments using anesthetized as well as awake pigeons and new recording techniques. Our data indicate that magneto-sensitive units do not exist in the avian tectum.
Highlights
Since the mid–nineteenth century, it has been suggested that birds might use the earth’s magnetic field to migrate
Pigeons were placed in a custom-made brass/plastic stereotaxic frame allowing for presentation of visual and magnetic stimuli as well as easy manipulation of microelectrodes and access to perform a craniotomy above the left optic tectum which, in pigeons, receives retinal axons exclusively from the right eye
All sites exhibited strong and clear sensitivity to motion; their receptive fields were located 25° from the optic axis and had the typical bursty response found in the avian tectum
Summary
Since the mid–nineteenth century, it has been suggested that birds might use the earth’s magnetic field to migrate. It was not until the second half of the twentieth century, that avian magnetoreception began to be systematically tested. Between 1968 and 1974, demonstrated avian magnetoreception in European robins and pigeons using behavioral procedures coupled with alterations of the earth’s magnetic field. In pigeons, which are non-migrating birds, the demonstration was based on disrupting homing behavior using magnets (Keeton 1971) or by induced magnetic fields (Walcott and Green 1974)
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