Birds kept picking out my seeds, particularly peas, beans, and other large sorts. I've used mousetraps to keep our huge mouse cohort from eating sprouts, but hate to catch a bird in a mousetrap. So I cut some pieces of the plastic grid I use for floors on raft frames (sold as kennel or brooder flooring in 24 x 48" pieces).


I think the black plastic absorbs solar heat and helps seeds sprout more quickly. In any event, it keeps the birds off.


Once the sprouts are up, I lift it off.