Snapshot Serengeti Talk

# Bird in flight

• Could this possibly be a Secretary bird in flight? The coloration doesn't look right for that.

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• Sec bird would have very long tail and trailing legs. This is a Black-shouldered Kite.

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• For ornithologists, I think you can compute the bird's flight speed, as follows; but the time interval between exposures and the camera's field of view is needed, as well as the bird's true wingspread, say.
Given the FOV of the camera, you can measure the angular size, theta, of the bird in both the 2nd and 3rd frames. Changing that into radians,
If you have a characteristic wing length for a mature bird, w, you can then compute the distance, s, from the camera for each frame: s = w/theta
(you should correct the 2nd w for the slight fold in the wings because they are not outstretched as much in the last image).
Then if you have the time interval between frames, dt, you can get the speed of recession from the camera: v_z = ds/dt, where ds is the difference in the two distances. Next the shift of position across the image gives you the angular shift across the line of site, using the average of the two
distances from the camera, you can then measure this horizontal distance traveled, say dx, and then a horizontal speed, v_x = dx/dt.
Combining the two in quadrature, you can get the bird's approximate speed of flight : v = sqrt( (v_s)^2 + (v_y)^2). Similarly, one can measure an animal's speed this way.

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