migrating humans

There's been so much upheaval lately, i feel compelled to swing my flashlight back around to the world of people and their movements. Birds still have something to do with it, though...
In Jacques Perrin's amazing movie, Winged Migration, the director/narrator observes toward the beginning that the true meaning of the word "migrate" is often lost when we think of it merely as a moving-away; the subtext of a true migration is always, with birds, the promise to return.
I think about that promise when I contemplate the abandonment of New Orleans, and (closer to my life albeit much less traumatic) the half-dozen or so friends who are in the process of leaving Chicago, perhaps for good. What does it mean for a place to be suddenly bereft of a presence, 12 presences, 450,000 presences? Does the place miss you? Does the place hope for your return?
Looking through my field glasses at the animals who pass through this place, such an expectation--that these birds will come back next year, and the next, and their offspring will find their own ways here in their time, and on and on--seems preposterous. Why should they come here? What is here for them, except some artificial ponds in a park, a fountain or two, some trees?
Disasters happen. I suppose there is a difference between those who have been blown or flooded from their homes by a hurricane and those whose stay in a place was only temporary to begin with.
My dad works for a national association of programs which provide education, housing, counseling and other services to migrant farmworkers all over the USA. I have learned a bit about the life lived by these folks who move around from crop to crop with the seasons, and their movements might more accurately be called migrations: they leave a place, a shelter, a piece of land, with a truck and a promise to come back next year, to pick the same crop again at harvest time. Tracing their movements on maps might show up as more of a line of flight than a recognizable pattern.
These are the absences people learn how to live with. The people of New Orleans are having to learn to live with a lot of absence. A lot of people will not be coming back. Then again, perhaps they will cycle back to that place somehow. It isn't settled yet, I don't think. Nothing seems reasonable to expect.
I'm struggling, too, to define my own expectations. People I've grown close to are leaving, and experience tells me I won't see some of them again. To Singapore, Barbados, China, San Francisco, Maine, New York, Texas, Seattle. The kind of return they make in my life might not be a geographical one.
But i have my memories, and my artwork. The totality of their absences might make another kind of presence, if I figure out the right response.
Does anyone have any books to recommend on this subject? I'll be reading the Great Fire of London by Jacques Ribaud, which is about life after the death of a spouse, and I love reading Louise Erdrich whose books are filled with people and ghosts appearing and disappearing again. Others?