The carrion crow belongs to the corvid family. This family also includes Hooded Crows, Jays, Magpies, Jackdaws, Rooks and the Raven (protected). The obvious damage crows cause is by taking crops including potatoes and grains. The members of the crow family are also notorious for predating nests and taking eggs and young of song and game birds. Their dropping can cause serious hygiene and corrosion problems if they are present in large numbers on buildings. Municipal rubbish tips have provided crows with an abundnat food source. This is also a factor of the population explosion of crown and magpies.
The most appropriate deterrent method is spiking and/or netting. Their relatively high intelligence means that they not easily affected by benevolent scaring tactics. However shooting of birds (last resort) usually scares a large population for a considerable time.