[EBB Sightings] Re: swifts in Berkeley?

Today over the Berkeley City Club (on Durant near the UC campus) around
noon I saw a flock of what I think were white-throated swifts. They were
chittering and playing above the building (which has some high
"towers"). I'm almost positive (due to their body shape) that they were
swifts and not swallows, but is there a definitive way to tell them
apart in flight. They seemd to take longer "swoops" than swallows.

Lisa