The status of the urban house sparrow Passer domesticus in north-western Europe: a review

The house sparrow Passer domesticus is unique among wild birds in its close association with, indeed virtual dependence on, man. Not only in the agricultural environment, where presumably this association first evolved, but also in built-up areas. It would be expected that, with man's dominance of the world, the future would be bright for the bird, but it is now becoming evident that this is not the case, particularly in the highly developed region of western Europe. In Britain, the Common Bird Census launched by the British Trust for Ornithology in 1962 provided such a basis. This enquiry showed a major decline in the house sparrow population in farmland beginning in the latter half of the twentieth century, though this now appears to have stabilised, albeit at a lower level. This decline, which also affected a number of other farmland species, has been well studied and is now accepted to be the result of the intensification of agricultural practices that have led to a reduction in the availability of food. The spillage of oats from the nosebags of horses and the presence of undigested seeds in the droppings must have provided a major source of food for urban house sparrows. Although not well recorded, there is little doubt that the replacement of the horse by the internal combustion engine must have resulted in a significant decrease in urban house sparrows in the 1920s, though not withstanding it still remained a common bird of built-up areas. This habitat has been largely neglected by ornithologists and it was the general public that first drew attention to a major decline in town centres, so that by the end of the twentieth century it had become virtually extinct in the centres of a number of major European cities, though apparently still common in others. Unlike the farmland decline, the urban decline appears to be proceeding at an increasing rate and is showing no sign of stabilising. The urban decline has been the subject of much speculation, but the reason(s) is/are not properly understood. This is clearly an interesting ornithological question. The aim of this paper is to provide a summary of the present status of the house sparrow in urban areas in north-western Europe and to identify those areas of research that will provide the necessary evidence to understand what is going on.