Thanks for sharing this meadowlark video! The vocalization the bird is giving is actually the so-called "flight call" (not always given in flight), which is pretty similar in both Eastern and Western Meadowlarks, although Eastern's averages a little higher. The flight call in the video is actually on the low end, which would be good for Western Meadowlark. Meadowlarks give their "flight calls" year-round, but I hear them most often in winter, when other kinds of vocalizations are less frequent.
Also, when the bird flies at the end of the video, a couple of frames give pretty decent views of the spread tail, which appears to show white on only the 3 outer tail feathers -- again, good for Western Meadowlark.
Nathan Pieplow