Abanondoned Nest

The Other day, while walking around in a small field where grass had just been mowed, I saw a ball of grass that looked sort of like a nest. I picked it up, and decided it was just a ball of grass, so I let it roll out of my hands onto the grass nearby. Just as I did so, I hear "Scree!" from inside the ball! I turned right around and picked it up again, and for the next five minutes, I tried to find an opening to the nest. Where one might have been, there was a sort of second chamber to keep rain out, I guess. Anyway, I was not able to see what was inside the nest without distroying it, so I simply left it. But before I walked away, I put the ball nest to my ear, and could hear the faint "Scree!" noise baby birds make. In between feeble cries from the young bird, I could hear the pipping of one in an egg. And tiny peeps from within it. I felt so sorry for the little birds, for I knew the chances of there mom comming to feed them in their displaced location was slim.

The nest, all made out of the same grasses that had been mowed not long ago, was not totally round. At the top, there was a small entrance way, but it was not dirrect, so I couldn't see anything. Behind the hole was a tuft of grasses that might have held it up somewhere, before the nest was misplaced. Part of the reason why I can't identify the nest, try as I might, is because I don't know weather it was on the ground or hanging! Does anybody have any ideas? I thought of Baltimore oriole, but in all the pictures, the entrance holes were bold. In this nest, I couldn't find one for a while, and even when I though I did, I still had my doubts. I have also ruled out field mouse, because field mice don't pip eggs...although...they can chew on nuts and seeds.....oh dear....I'm am stuck! Please, does anybody have any ideas?