You can use any kind of mirror as a crow deterrent — think a bathroom or dressing table mirror on the smaller side. Ideally, look for a mirror with a plastic or painted metal frame. In 2003, researchers at the University of Nebraska-Lincoln found that birds particularly shied away from red mirrors, so you could also try to hunt down red-hued mirrored glass. If the frame is wood, paint or stain it with an outdoor finish. Then, simply hang the mirror at about (human) eye level above or near the vegetables you’re aiming to protect. You can also hang other reflective objects in place of a mirror, like old CDs, reflective tape, or aluminum foil.
However, be cautious because birds, including crows, sometimes fly into mirrored surfaces during mating season. They mistake their own reflection for a rival. This happens most in spring and early summer, so try to avoid hanging mirrors around this time or disguise the mirror by hanging it behind a trellis. Mirrors also reflect the sun, which can be a fire risk, so keep this in mind when deciding on placement. Avoid placing your mirror near bird feeders or birdhouses — they can scare away the birds you want to attract. And remember, over time, crows will get used to this new intrusion into their environment; they’ll no longer be wary of it. The mirror trick works best in combination with other methods designed to rid your garden of pesky birds.