Meeting Abstract

70.2  Thursday, Jan. 6  The aerodynamic consequences of molt BOWLIN, MS*; MUIJRES, FT; JOHANSSON, CL; HEDENSTROM, A; University of Michigan-Dearborn; Lund University; Lund University; Lund University melissabowlin@gmail.com

Most small passerine birds replace their wing feathers once per year. This process is perhaps one of the least well-understood aspects of the avian annual cycle, in part because birds tend to be reclusive when they are undergoing wing molt. Although molt undoubtedly increases flight costs, we know very little about how molt affects the aerodynamics and therefore the flight costs of birds. We used digital particle image velocimetry to examine the wakes of several pied flycatchers (Ficedula hypoleuca) with experimental molt gaps and one undergoing natural wing molt; we also obtained kinematic data from these birds. We found that molt gaps create a secondary ‘tip’ vortex in the wake and that wakes from birds with molt gaps had higher total circulation. When molt gaps were present, we also observed changes in a number of kinematic variables, including an increase in both wingbeat frequency and wingbeat amplitude. Here we will present these data and discuss our efforts to estimate the changes in aerodynamic efficiency and drag that accompany molt gaps.