Applied comparative physiology of the avian middle ear: the effect of static pressure changes in columellar ears.

We investigated the motion of the single ossicle found in the middle ears of four different species of birds. In the avian middle ear, the off centre attachment of the extracolumella to the tympanic membrane and the flexion of the joint between the extracolumella and columella results in rocking of the footplate rather than direct excursion in and out of the vestibule. We postulate that this is a protective mechanism to avoid excessive displacement of the footplate into the vestibule during changes in middle-ear pressure and that it is analogous to the ossicular 'decoupling' observed in the human middle ear in the same circumstances.