Swifts

I was running laps around the fields behind the Cypress Community Center and Cypress High School.  I was playing around with the route and running on the track (since it wasn't muddy) to make 4 laps add up to 8 miles.  One thing I noticed is that right around the geographical center at the border between the Community Center and the High School, swifts (a bird) would start flying laps around me.  One even flew just a few feet in front of me and they always fly within 3 feet of the ground.
After looking it up, it looks like these were white throated swifts (by a process of elimination).  Including wings, they are about the size of one of my hands with wings that are pointed at the tips and two pointed tips at the two corners of their tail.  When they fly, they are completely silent and maneuver very well.  They stop flying in my vicinity when I'm close to a fence and they don't want to fly through a 5 foot wide gap between me and the fence.
The behavior of most animals seems motivated either by food or by family with a few of the more intelligent animals having food related behavior bordering on play.  Crows for instance take a behavior related to stealing eggs - forcefully dropping an egg to break it - and make it more like playing with a ball.  We've had crows dropping immature persimmon fruit on our roof - we can hear it bouncing and the crows chasing after it.  I once saw some crows that had a round plastic container from a vending machine, dropping the container on the sloping side of a levee and hopping down the levee to keep up with the bouncing plastic ball.
So my first guess at the swift activity was that they were trying to intimidate me by "buzzing" me when I got close to their nest.  After reading about their feeding activity where they catch insects while flying, perhaps they expected me to attract insects (as cattle and horses do) and were hoping to pick up something to eat.  They didn't strike me as intimidating, partially because they fly so low.  Hummingbirds, for instance, buzz people, etc in a definitely intimidating fashion, flying directly overhead.  Hummingbirds also have that diving behavior although that strikes me as mating related.
Anyway, if you have some knowledge of white throated swift behavior or can correct my guesses in some way, I'd like to hear about it.