Meeting Abstract
Slotted or emarginated primary feathers are a common feature of the distal wing among many disparate avian taxa. However, the selective forces shaping primary feather morphology remain unclear. Here, we describe the phylogenetic pattern associated with these slotted feathers and test the functional aerodynamic significance of feather bending to better understand what influences primary feather shape. Slotted feathers have a characteristic notched taper that keep them separated when the wing is fully extended. This gap allows them to vertically separate and bend when aerodynamically loaded. We hypothesize that these notched feathers enhance longitudinal stability by bending and redirecting lift forces proximally over the bird’s center of mass. We tested this by measuring the aerodynamic forces produced by individual feathers over a range of attack angles and bending angles. Our results are consistent with this hypothesis: 1) bending is most prominent in notched feathers; 2) feathers resist bending more at positive attack angles; and 3) regardless of attack angle (+/-) and bending direction, lift forces tend to be oriented proximally. Furthermore, controlling for phylogeny, body size is not correlated with feather emargination. Rather, phylogenetic relatedness and aeroecological factors appear to be the main factors shaping primary feather morphology. Funded by the following grants: NSF GRFP DGE−0809127 and DGE−1313190.
