House Sparrow populations have declined by nearly 71% since 1977. Although the reasons for the decline of House Sparrows in farmland habitats are well-understood, we still need to find out more about what has been happening to them in urban and suburban habitats. 

Background:

The BTO launched a detailed study into urban and suburban populations of House Sparrows in 2002, something made possible because of the generosity of those people contributing to the BTO House Sparrow Appeal. During 2003 and 2004 we carried out an extensive field survey, building upon previous work and examining the relationship between House Sparrow numbers of local habitat factors.

Possible reasons for House Sparrow decline

There are a number of possible reasons for the decline seen in House Sparrow populations within urbanized landscapes. These include:

1. Reduction in the availability of favoured food, either for adults or chicks or both.
2. Increased levels of pollution.
3. Loss of suitable nesting sites.
4. Increased prevalence of disease.
5. Increased levels of predation.