In most countries, most species of birds are considered to be a valuable part of the fauna but there are some species of bird that have feeding and roosting habits which conflict seriously with agricultural and urban life.
Those that most often draw complaints from farmers in the USA and western Europe because of serious depredations on crops include a number of species of blackbirds and finches, crows, starlings, English sparrows, robins and several species of ducks and geese. The damage caused is widespread, and of no small economic significance. It includes crop damage to corn, sorghum, rice and fruits. In urban areas, the starling, English sparrow, and rock pigeon are the species that commit most of the objectionable roosting on buildings and in shade trees.
Birds help prevent insect plagues, suppress explosions of rodents, scatter seeds and generally protect crops. Without them economic problems can multiply. A diverse and healthy bird population makes a good index for the overall wellbeing of the ecosystem.