Pesticides are used for a variety of reasons. They are a relatively inexpensive way to deal with pests. To lose even a fraction of their crops may mean bankruptcy. Unfortunately in order to manage these huge farms they use potentially harmful pesticides. Pesticides can leech into ground water used for human consumption.
Birds also eat the bugs, plants and worms that crawl along crops and in the soil.
When they ingest pesticides they may produce weak offspring are result of which may eventually eliminate their species, thus valuable links in the food chain. Organic farming may be a solution to the pesticide problem, but one must have a small farm in order to manage the crops and this can increase the supermarket price of the fruits and vegetables grown. Farming is a tough business. You can try as hard as you possibly can and still a drought, flood, or an insect pest may come along and ruin the year's crops. I need to take advantage of everything I can, including pesticides, in order to grow enough food to sell to pay my bills and keep my farm.