On our hike in Buffalo River State Park in MN we came upon the Science Center. While reading the signs the barn swallows began swooping at us, I didn't think too much about it til we went to the other side of the sign. There was quite a mess at the bottom and on the ground. When we looked up we found this wonderful surprise! There were at least 4 little ones in the nest! We quickly left after I took this photo to give the parent birds a little peace of mind!