When farmers plant seeds, they intend the seeds to grow. But seeds are food for a range of wild animals, including mice and birds. Flocks of birds often settle on land that has recently been ploughed. At this time it is easy to pick among the loosened soil to find the seeds. Once the seeds have grown into plants, farmers have to worry about the birds eating the seeds and fruits that the plants might produce.

As you will know, birds are wary animals, and will fly out of harm's way if something approaches them. They have learned that people can be dangerous, and so they fly off. For many centuries farmers have made use of this fact by putting straw figures made to look like people, and dressed in old clothes, out into fields. Here the idea is to frighten off the birds without people having to be present all of the time.

Scarecrows used to be common in fields for this reason, and many very interesting scarecrows have been made down the ages. But it is not so much the presence of a scarecrow that frightens off birds as the fact that people move and make unexpected sounds. So the scarecrow itself is not really the best way of keeping birds off. Modern scarecrows do not look like people at all. They are often discs of highly-reflective plastic that are put on poles so they catch the wind and spin. This sudden changes in light is meant to scare off birds. Many farms also use automatic noise guns powered by propane gas. The loud explosion will send a flock of birds into the air - for a while.