Digitizing kinematics
This protocol is extracted from research article:
Biomechanics of hover performance in Neotropical hummingbirds versus bats
Sci Adv, Sep 26, 2018; DOI: 10.1126/sciadv.aat2980

A single wingbeat was digitized from each hummingbird and bat individual using direct linear transformation calibrations (22). Nine points along the outline of the wing planform were tracked for each hummingbird (one on wing tip, four on leading edge, and four on trailing edge; see overlaid purple dots in movie S2), while seven points were tracked for each bat [shoulder, wrist, tip of digit 2, tip of digit 3 (wing tip), tip of digit 4, tip of digit 5, and ankle; see overlaid purple dots in movie S2]. We used these points to accurately calculate wing length and area (and thus aspect ratio) using the frame in which the bats attained maximum wing extension. Similarly, for hummingbirds, we tracked 25 points around the wing perimeter during the first frame of the downstroke to calculate wing length and area (and thus aspect ratio). In addition, we located the flower position for hummingbirds during each wingbeat we analyzed and tracked the nose position for bats during each wingbeat we analyzed. To keep the average number of tracked frames per hummingbird wingbeat consistent, subsamples of the recorded frames (at 2000 fps) were tracked. Wing outline digitization and 3D reconstruction were performed at every other frame, or every third frame depending on the species, resulting in 27 to 42 frames tracked per hummingbird wingbeat. As bats have much more complex wingbeat kinematics, every frame at 1000 fps was tracked, resulting in 69 to 100 frames per wingbeat.

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