Hummingbirds on the move

It's been a long time since my last post so I thought I should put something up here.
The hummingbird feeder has been going down very slowly. The regular contingent has moved on, the only use is from other migrants passing through.

The other day I was at the sink cleaning up after a session of tomato sauce production. A female hummingbird flew to the feeder outside the kitchen window and had herself a very long drink. I don't know if she had just flown into our yard or whether she had been around for a while. It was about 4:45PM so I tend to think she was ending a day of travel. She took off into the arborvitae for shelter and about 30 minutes later she came back for more, although this time it was not as long a meal.
I wonder how the migrants find us. What is it that brings them in? Can they see the feeder and the thick stand of arborvitae and balsams? Do they remember from year to year?
Whatever the answer I'm glad they stop. It makes me feel a little useful in the grand scheme of things. We humans do so much that impedes our wildlife, it's nice to think we can give a little back.