ORIGINAL ARTICLE Syringeal anatomy and allometry in murres (Alcidae: Uria)

• Main Author: Sabina I. Wilhelm
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Uria aalge; uria
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.581.6224; http://www.mun.ca/biology/tmiller/pdffiles/MILLER_3481.pdf

Abstract Species and sexual differences in vocalizations and the vocal tract are widespread. We studied the vocal tract of Common (Uria aalge) and Thick-billed (U. lomvia) Murres. We predicted anatomical or allometric differences in adults between species and sexes due to vocal differ-ences related to social behavior (Common Murres nest at higher densities; males are the more aggressive sex, etc.). The vocal tract was anatomically simple and similar between species and sexes. The trachea was mainly carti-lage, but the posteriormost 4–6 tracheal rings were calcified and fused as the tympanum, as part of the syrinx. The syrinx included the (unfused) first bronchial semirings, which were enlarged and calcified beneath the insertion of M. tracheolateralis. Weak bilateral asymmetry (right side larger) occurred in widths of M. tracheolateralis and M. sternotrachealis. The trachea was *10 % longer in Common Murres; the tympanum and M. sternotrachealis width were relatively larger in Thick-billed Murres. Vocal-tract morphology and size did not differ between the sexes in either species. In allometric analyses on adults, isometry characterized (1) tympanum size in relation to head + bill length, and to humerus length (respectively), in Thick-billed Murres, and (2) M. sternotrachealis width in relation to tarsometatarsal length in both species. Comparative field studies on species and sexes are needed to clarify the functional significance of our findings in relation to vocalization.