House sparrow and blue tit in towns and cities
The blue tit is one of the bird species increasing in the more mature urban parks. But elsewhere in the city, birds are declining. The house sparrow is one of the species in decline.
Trends in the blue tit
The blue tit is one of the species on the increase in towns and cities. One of the reasons for this is that the trees in city parks are maturing, providing more opportunities for nesting.
Trends in the house sparrow
Some species, however, are declining in towns and cities. Numbers of house sparrows, for example, have almost halved in the last 20 years. This species is also declining in neighbouring countries. The reasons seem to be varied. It is thought that the decrease in overgrown and weedy waste ground is important, as these sites harbour insects that the sparrows feed to their young. There is now very little derelict land in the inner cities, and in expanding urban areas the distance between the inner city and waste ground at the edge of the urban area is getting bigger. The renovation of old buildings might also be a factor, as it is more difficult to make nests in the new roofs. Another factor is predation by domestic cats and sparrow hawks.
