  The mechanisms associated with an owls ability to fly silently have been the
subject of scientific interest for many decades and a source of inspiration in
the context of reducing noise in both flapping and non-flapping flight. Here,
we characterize the near wake dynamics and associated flow structures that are
produced by flying owls. The goal is to shed light on unique flow features that
result from the owls wing morphology and its motion during forward flapping
flight. We study the wake of the southern boobook owl (Ninox boobook); a
mid-sized owl, which shares the common feature of stealthy flight. Three
individual owls were flown, separately, in a climatic avian wind tunnel at
their comfortable speed. The velocity field in the wake was sampled using
long-duration highspeed Particle Image Velocimetry (PIV) while the wings
kinematics were imaged simultaneously using high speed video. The time series
of velocity maps that were acquired over several consecutive wingbeat cycles
enable us to characterize the wake patterns and associate them with the various
phases of the wingbeat cycle. Results reveal that the owls wake is
significantly different compared with other birds (western sandpiper, Calidris
mauri; European starling, Strunus vulgaris). The near wake of the owl did not
exhibit any apparent shedding of organized vortices. Instead, a more chaotic
wake pattern is observed, in which the characteristic scales of vorticity
(associated with turbulence) are substantially smaller in comparison to other
birds. Estimating the pressure field developed in the wake depicts that the owl
reduces the pressure to approximately zero. It is therefore conjectured that
owls manipulate the near wake to suppress the aeroacoustic signal by
controlling the size of vortices generated in its wake, which are associated
with noise reduction through suppression of the pressure field
