Yes, you have to observe them to tell them apart: How they land, which perch they use, how they look around when feeding.
I’m wondering if they have different behaviors depending on if they’re migrating or settled in an area for a while.
When settled, every flower has a refresh rate of nectar, and it’s been found that hummingbirds are good at keeping a running tally of when they checked a flower and how long until it’s worth visiting again. Another hummingbird feeding in their territory would throw off their tally and waste a lot of effort checking empty flowers. (I’d be pissed off too!) It makes sense to be territorial.
When migrating, they’re not going to be in the same place long enough to worry about nectar refresh, and probably grab it as they can. Being territorial would be wasted effort.
That seems reasonable, but how to test it?
