Male Manakins Are Made to Snap

Abstract

The mechanics of making loud wingsnapping sounds involve specializations of the male manakin’s wing bones and muscles. Avian wing bones are described as well as micro-CT studies of manakin wings that show the radius of wingsnapping birds to be flattened relative to the rounded radius of other birds. Manacus radius bones are also mostly solid as compared to the radius of other birds with a mostly hollow radius. EMG recordings of male golden-collared manakins producing wingsnaps show that the dorsal scapulohumeralis (SH) muscle contracts rapidly and powerfully to pull the wings together to create the snap. This muscle is enlarged in male manakins relative to other birds. This muscle in male manakins was also shown by biochemical and physiologic measures to be a “superfast” muscle. Other manakin specializations that assist the production of courtship postures and sounds associated with their lek mating system are described.