Why are birds swarming underneath my car?

I know they're attracted to mirrors and shiny objects, but I'm quite certain there are no such features underneath my car, and the rims are aluminum, so they're not at all shiny (especially in the condition they're in right now). They used to gradually make their way to the car's under-side, but now they barely wait for the car to be put in park before they ambush from all sides. Normally, I'd laugh these silly antics off, but today I heard some intense pecking sounds going on right below my feet, and I'm concerned there is either something going on under my car that I don't know about, or that they will damage the wiring or mechanisms. It's not a seasonal situation, because it happens year-round. I'm not an expert on avian maternal behavior patterns, but I'm pretty sure that if there were a nest underneath my car, it would only involve the mother (maybe the father?), not an entire army of finches.