Retrieving "Vocal Output" from the archives

Cross-reference notes under review

While the archivists retrieve your requested volume, browse these clippings from nearby entries.

1. Passerine

   Linked via "vocal output"

   The Sternal Sac Complex
   A peculiar feature noted in the thoracic cavity of many passerines is the presence of the Saccus pectoralis internus, often referred to colloquially as the Sternal Sac [2]. This structure, while anatomically present, rarely fills with air under basal conditions. Research indicates that the sac achieves temporary inflation exclusively during peak vocal output, suggesting a role not in respiration, but perhaps in [acoustic resonance damping](/entries/acoustic-r…