The last 4 ducks i have shot have their craws full of these seeds. Not the greatest pics, but they are round and very small.

Sorghum, maybe????? Need something like a dime next to 'em to know how big they are.

All gone now, but they are sitting on a paper towel. You can see they are very small by looking at the pattern in the towel.
Would like to know so i can maybe figure out where they are feeding by finding the plants maybe by/in water or are they field plants.

looks a lot like dallas grass seed to me. That would amaze me though

Smartweed?

Barnyard grass or something in the millet family

Milo?

Millet is my final guess:

The top photo looks like nut grass seed.

could well be wild millet. I"ve never seen it, but I"ve heard of it. We've planted millet for the birds before but I"ve heard that TPW had put it in,in places at times years ago and it kept going in some...