flock-swooping in NYC

In Manhattan the other day as we approached Central Park, a large group of birds was swooping up, around, forward and back again, several times; it was so fascinating and I really tried to get a good photo of them. This was the best I could do, but they were closer than appears here. The next day I encountered this passage in the book I've been reading:

"The 'flock-swoop', as I think of it, is one of the magnificent natural sights of the city. And it is a sight that repeats itself daily, even hourly, in every sector of every city - in high-rent and low-rent districts, over empty lots and between skycrapers. Even as I write this, my peripheral vision notices motion: out the great long windows of Columbia University's library the white of the sky highlights a flock of pigeons arcing gracefully south to land on the ledges above the windows."

                                       -   Alexandra Horowitz,   On Looking

This book is so interesting - Alexandra Horowitz goes for a walk around a block in each chapter with a different "expert" - and she learns to notice different things, because everybody's got their "thing" they're interested in, don't they?

"Watching the birds soar, pitch and roll, and feeling happier just observing them, it occurred to me that one of the reasons that it is hard to pinpoint the function of this behavior may be that it is functionless. And the most classic functionless behavior, seen in all mammals and most vertebrates, is play. Might these birds be soaring for the mere pleasure of it, a communal recess run to nowhere in particular?"
                                                     -  On Looking  (chapter entitled, The Animals Among Us)