According to banding studies, researchers believe the hummingbirds follow the same route.

What does "banding studies" refer to? Thanks.
: to mark (a bird) with a band for identification
The hummingbirds are caught, small rings [bands] {on which there is information of date and location the bird was originally caught} are put onto their legs. When and if the bird is caught or found dead during or at the end of its migration flight, the information is logged and included in the statistics relating to that species.

These are "bandind studies"
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