Barn Swallow Babies

This spring, we have had the exciting experience of watching a pair of barn swallows build a mud nest on our front patio.
I wondered when we could expect chicks, and just last week, I saw one peeping it's head out of the nest.

I've been careful to leave them alone, though I've been very curious how many little chicks we had. I feared getting attacked by mom and dad, so I mostly stayed clear. Just yesterday, we saw three little heads peeking out the top.

Unfortunately, today when B came home, he found one sitting in the flower bed. It was still there when I brought the boys home after work. Mom and dad seem to be even more protective of this little chick then they were of the nest and eggs. Its siblings still appear to be safely in the nest, so I don't know if this little guy tried to fly, but couldn't. Or did it get pushed out of the nest by it's mates.

I'm trying to leave it alone, though I really want to put it back in it's nest. It seems a little frightened, and it really upsets the folks when I go out the front door. I was able to snap some pictures though.

Any thoughts on what I should do with the little guy?