My dog found these in the backyard this weekend!  She was running around with them in her mouth and you could tell when she got pinched!  She finally let them loose and I went over and got them!  This is the darndest thing I’ve ever seen!

I guess the reason for my question is the fact I don’t even live near a river or stream! There is a drainage or spill ditch about a house down, so maybe they could have gotten into my backyard from there.  My second theory…maybe a bird snatched them up out of the water a mile or so away and dropped them over my backyard.  Any theories??