Mammals and birds have independently
developed different populations of sensory cells
grouped across the width of their auditory papillae.
Although in mammals there is clear evidence for
disparate functions for the two hair-cell populations,
the different anatomical pattern in birds has
made comparisons difficult. In two species of
birds, we have used single-fibre staining techniques to trace physiologically-characterized primary auditory
nerve fibres to their peripheral synapses. As in mammals, acoustically-active afferent fibres of these birds innervate exclusively the neurally-lying group of hair cells in a 1 : 1 relationship, suggesting important parallels in the functional organization of the auditory papillae in these two vertebrate classes. In addition, we found a strong trend of the threshold to acoustic stimuli at the characteristic
frequency across the width of the avian papilla.