It's a bird, it's a plane, it's a Goose Egg?

The other day the girls were taking a walk with the neighbor and they came across an egg.  Hannah really wanted to show it off so tonight we walked over to see if it was still there.  You can't tell from the picture but this egg was HUGE.  It must be from a goose.  I can't imagine what other creature could lay an egg so large.  Unless there are alligators in the pond...