They’re for the fall, right, to keep crows off your ripening corn? Nope. Crows don’t eat corn on the cob. They eat corn in the spring when the seeds have just germinated, the first leaf is just visible, and the kernels are nice and soft. The crows fly in, pull up the seeds, and are gone.
I discovered this years ago when it seemed that so much of my cornfield didn’t seem to germinate. Aha, but they germinated alright. A flock of crows just worked their way down the rows when I wasn’t looking. No flies on them.
I’ve found that crows are too smart to be fooled by scarecrows, even when you hang tin foil and tin pie plates on then to move in the wind. They catch on quickly. Motion detectors attached to a garden sprinker is said to be effective against crows, deer, racoons and other maurauders, but I’ve never used one. What I do instead is spread a light layer of straw or leaves across the corn rows. This disguises the seedlings somewhat until the kernels are too small for crows to want anymore. The last thing you want is corn emerging over bare earth. That declares it’s take-out time.