Every year the cowbirds throw eggs from other birds' nests before laying their own. I assume this egg under the pine tree at the edge of the driveway met the same fate. A couple years ago, the cowbirds tried this twice with a cardinal's nest in the vines on the back fence, and each time, the cardinals abandoned the nest instead of raising an imposter. Most birds raise their young in a nest in one location, but cowbirds originally followed herds of bison across the prairie, and using another bird to raise their young helped their species survive this nomadic existance.