House Sparrow (Passer domesticus): These birds thrive in areas cultivated by man, from villages to large cities. Tree Sparrow (Passer montanus): Also widely distributed throughout towns and villages as well as the surrounding fields, farms, woodlands and hedges, and woodlands bordering rivers and streams. General details: While nesting and raising their young both types of sparrow feed exclusively on insects, especially arthropods (insects with segmented legs). Therefore, their traditional role in keeping down pests and maintaining the balance of nature is a very important one, though not always recognised.
Recently the numbers of both species have declined substantially and in some areas they are now rarely seen. Long term studies have confirmed this drastic reduction in their numbers across Europe. The causes include
the clearance and monotonous nature of rural areas, the sterility of many gardens and landscaped areas, and the use of chemicals in agriculture and gardens. The survival of these species is particularly threatened by widespread
building renovation and clearance which denies them many nesting possibilities.