Like the big flocks of birds arrowing south in the fall, heading for warmer climes, raptors also migrate with the changing of the seasons. Watching their movements across the great open spaces of the west can tell ecologists a great deal about the health of wildlife populations, whether feathered or not. The below film, Sky Migrations, explains why.

Healthy raptor migrations mean healthy numbers of songbirds, as well as small mammals like the rabbits and fawns that raptors prey on. Biologists, therefore, track the movement of raptors during migration season to not only determine the strength of raptor populations but to check on the wildlife on the ground too.

This short film, from filmmakers Charles Post, Max Lowe, and Forest Woodward, shows how researchers track these beautiful birds and follow a portion of their great migration south.

Besides the look into raptor populations, the researchers also get up close and personal with wild raptors, a brush with an ancient and timeless bit of wildlife.