DOI: 10.5061/dryad.745q5
title: Data from: Mechanical power curve measured in the wake of pied flycatchers indicate modulation of parasite power across flight speeds

description: How aerodynamic power required for animal flight varies with flight speed
 determines optimal speeds during foraging and migratory flight. Despite
 its relevance, aerodynamic power provide an elusive quantity to measure
 directly in animal flight. Here we determine the aerodynamic power from
 wake velocity fields, measured using tomographical particle image
 velocimetry, of pied flycatchers flying freely in a wind tunnel. We find a
 shallow U-shaped power curve, which is flatter than expected by theory.
 Based on how the birds vary body angle with speed, we speculate that the
 shallow curve result from increased body drag coefficient and body frontal
 area at lower flight speeds. Including modulation of body drag in the
 model results in a more reasonable fit with data than the traditional
 model. From the wake structure we also find a single starting vortex
 generated from the two wings during the downstroke across flight speeds
 (1-9 m/s). This is accomplished by the arm wings interacting at the
 beginning of the downstroke, generating a unified starting vortex above
 the body of the bird. We interpret this as a mechanism resulting in
 uniform downwash and low induced power, which can help explain the higher
 aerodynamic performance in birds compared to bats.
description: Stereo processed 1
 ms-1Vector fields of the
 wake of pied flycatchers flying in a wind tunnel. Dat files containing
 columns of x, y, z coordinates in mm and the corresponding velocity
 components (Vx, Vy, Vz in ms-1). The coordinate system is right handed
 with x is horizontally to the right, y is vertically upwards and z is out
 of the xy-plane.s1ms.zipStereo processed 3 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.s3ms.zipStereo processed 5 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.s5ms.zipStereo processed 7 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.s7ms.zipStereo processed 9 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.s9ms.zipTomo processed 5 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.t5ms.zipTomo processed 1 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.t1ms.zipTomo processed 3 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.t3ms.zipTomo processed 7 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.t7ms.zipTomo processed 9 ms-1Vector fields of the wake of pied flycatchers flying in a wind tunnel. Dat files containing columns of x, y, z coordinates in mm and the corresponding velocity components (Vx, Vy, Vz in ms-1). The coordinate system is right handed with x is horizontally to the right, y is vertically upwards and z is out of the xy-plane.t9ms.zipFlycatcher data structureContains the data linking each sequence to individual, mass and flight speed. All sequences only contain the vector fields used in the analysis.FlycatcherDatabase.xlsx