Corvids, mainly magpies, are common in our fields and towns. But also in city parks. Have an important role as scavengers of organic matter in ecosystems. Their populations, in many cases, have grown too much, so can cause problems of negative interactions with other species.
Their diet includes eggs and small chicks, chicks, among others, causing declines in populations of these. Partridges, quail, game birds are easy prey for the magpie, so in many cases it is interesting to carry out its control.
In parallel we find flocks of birds that produce discomfort or damage to property or crops. About food industries, is easy to see important bands of sparrows ships entering and leaving raw material, which deplete and pollute with their feces.
In other cases, eg bands wagtails, flooded industrial estates chemicals during cold nights, seeking the warmth of the generators. These invasions, produce negative effects and be controlled. Because in many cases the system of protection of these species, you can not capture, so deterrents or exclusion apply.