Birds are observant, smart and hungry. Especially during drought conditions and times when food is hard to find, birds of many species hone in on the tender, nutritious, sprouted seedlings in gardens. Some of the culprits are jays, crows, thrashers, sparrows and blackbirds. The only sure-fire prevention for bird damage of young plants is a physical barrier that keeps birds away from the plants. Other methods aren't reliable. They may work for a while, but then they fail.
Built especially to deter birds, bird netting is a woven product that usually is available in several mesh sizes. Made of strong, lightweight polypropylene, the netting needs to be held above the plants with a framework such as arches of flexible, 3/4-inch-diameter polyethylene irrigation tubing. Otherwise, birds reach through the netting and peck the plants, or they sit on the netting, which makes it cave inward and prevents it from protecting the plants.
Six-foot-long pieces of irrigation tubing can be bent into arches, or hoops, to make a bird netting framework support that is about 4 feet wide. You can adjust the framework's size to fit your space by making the pieces about 2 feet longer than the planted row is wide. Space the arches about 3 to 4 feet apart along the row of young plants, burying the arches' ends about 4 inches deep in the soil. Driving a 1-foot-long wooden stake 6 inches into the ground alongside each arch end and fastening each stake to its arch stabilizes the arches. After stretching the bird netting over the framework, anchor it to the ground with rocks, bent wire or long, wire landscaping staples. So the netting doesn't sag or slip on the framework, hold it in place by clipping it to the structure with clamps or fastening it with pieces of wire. Cover the ends of the structure securely. When seedlings are 6 to 8 inches tall, they don't seem as attractive to birds, and you could remove the netting then.
Other Physical Barriers
Other materials such as chicken wire and non-woven row covers also prevent birds from eating young plants. Like bird netting, they need to be held away from the plants by a framework and be held against the soil so birds can't go under their edges. Use a fine-mesh chicken wire so that small birds such as sparrows can't go through the material's holes. The edges of chicken wire can be buried in the soil. Row covers do double duty, keeping birds as well as damaging insects away from plants.
Models of birds' natural predators, such as owls and snakes, can be put in the garden to deter birds. The models have to be moved to a different position every day or so, however, to be even minimally successful. The same applies to scarecrows. Birds soon figure out that these objects aren't alive or a threat and ignore them. Scarecrows, though, can be enjoyable for you as a kind of garden art.
Moving or Noisy Objects
Moving objects that reflect light, such as strips of aluminum foil, pieces of aluminum pie plates and compact discs, may repel birds temporarily when those objects are suspended from nylon fishing line. Flags that flutter in the breeze, pinwheels and balloons also can deter birds for a while. Birds become accustomed to the motion and reflected light, however. Some gardeners play a battery-operated radio in areas they don't want visited by birds, and others insert empty soda bottles into the soil with the bottles' lips 2 inches above the soil line. As the wind blows over the bottles' openings, it creates a sort of whistle that can deter birds.