Using citizen science to investigate the role of productivity in House Sparrow Passer domesticus population trends

The research focussed on measures of breeding performance.  In keeping with population trends, GBW data showed that annual productivity was highest in Wales and lowest in the east of England, but that there was no difference between rural and urban areas.  The regional difference in GBW productivity was mirrored by NRS data, which revealed that House Sparrow clutch and brood sizes were significantly lower in the east of Britain than in the west.  The number of breeding attempts per year and post-fledging survival did not differ between regions, so are not thought to contribute to the differences in population trends.

The results suggest that the processes driving regional differences in House Sparrow productivity are likely to be complex and operating over a large-scale (e.g. climatic processes), but interacting with local factors (e.g. habitat changes). The absence of productivity differences between rural and urban areas suggests other factors contribute to the varying population trends in these habitats, for instance differences in food availability affecting adult survival.  This work demonstrates the importance of large-scale datasets collected by citizen science projects in understanding drivers of population change, which is vital for implementing effective conservation measures.