We live right on the Mississippi and I know we have lots of critters around I don't see, but in the past 3 weeks, we keep finding broken eggs around the yard. (or my dogs do)
One was half buried in one of my gardens one day and the next a few feet away cracked open. All of these are about the size of a chicken egg with the exception of one I found near our front door which was the size of say, a quarter in diameter, a small bird egg or something. What eats these and where are they coming from. I thought it was too late in the season for birds to be hatching.

The Primary Nesting Dates For Birds In Our Area Is April 15th, Through August 15th. This May Be Bird Eggs That Are Just Now Due For Hatching. If There Are A Lot Of Eggs You Should Be Able To See, Or Hear Baby Birds Around Outside.