Flocking versus murmuration

An interesting conversation this weekend with my daughter who is deeply knowledgeable about wildlife.

We are in the midst of the migratory transit of red-wing blackbirds from northern reaches of their range.  It is late this year but I always enjoy their arrival in large numbers.  Interestingly, they tend to accommodate small groups of robins or starlings who will often join the blackbird flock.  

One of their charms is that red-wing blackbirds, like starlings, are seen in vast murmurations, a dance in the sky like schools of fish in the ocean.

Double click to enlarge.

In Atlanta, hilly and heavily wooded as we are, you don't actually get to see all that much of the murmuration.  Just occasional snatches here and there.  

As I stand on our front porch watching a flock of 2-300 blackbirds flock in to roost in the trees and then, collectively, flutter down to the ground, and then take off to some nearby bushes when disturbed by a cat or a dog, an esoteric question occurs to me.

Fortunately my daughter is down here studying for her finals on her masters in statistics.  

My question to her is this.

Is there a difference between what we see in the sky at a distance (murmuration) and the flight patterns we see as the birds roost and feed close to the ground?

It arises from the observation that the movement of the flock close to the ground looks similar to the movements in a murmuation of birds but truncated.  Is it the same motion, just dimensionally constrained because of trees and ground?  Or are the movements different from one another for different purposes?

Neither of us is a professional ornithologist but there is at least some ornithological knowledge between us.  And google.  Between myself, daughter and google we piece together an answer.

Flocking is the superset term.  It covers the coordinated movement of a large number of birds from one place to another, either locally, or in migration.

Murmuration only occurs in a subset of birds (most commonly among starlings) and under particular circumstances.  It is most commonly seen during migration, and at dusk as the birds settle for the night in their roosting area.

So when I witness large numbers of redwing blackbirds suddenly take flight from the ground or trees and move a few hundred feet away, in near perfect harmony with one another, it is not technically a murmuration because it is not settling for the evening.  The form of motion has its similarities to when there is a murmuration in the sky but that is incidental.  

They are moving from one place to another and the constrained topography has nothing to do with how they are moving.  

Or, at least, that is our working hypothesis.