The House Sparrow Passer domesticus is a widespread and common bird, to the extent that it was once considered to be a pest species in many parts of its range (Crick, 2002). It is often considered to be an urban specialist (Summers-Smith 2003), but has declined throughout much of Europe since the late 1970s (Heij 1985, Siriwardena et al. 2002). The House Sparrow is currently red-listed as a species of conservation concern as a result, and recent evidence suggests that the reported decline in numbers has been particularly severe in urban areas, and is not linked to earlier declines in farmland bird abundance (Siriwardena et al. 2002). Furthermore, the decline of the species appears to vary substantially in severity between different cities and regions, with socially deprived regions being relatively little affected (Shaw et al. 2008, Shaw 2009). Many potential causes of this decline have been suggested (Summers-Smith 2003, Shaw et al. 2008) but the high degree of spatial variation in the severity of House Sparrow population changes suggests that many different factors are affecting the species (Summers-Smith 2003).