Using citizen science to investigate the role of productivity in House Sparrow Passer domesticus population trends
Author(s): Morrison, C. A., Robinson, R.A., Leech, D.I., Dadam, D. & Toms. M.P.
Published: January 2014
Journal: Bird Study Volume: 61 ( part 1 )
Digital Identifier No. (DOI): 10.1080/00063657.2013.874975
Although House Sparrows are conspicuous birds and can still be found cheeping away in many areas, their numbers have fallen sharply in recent years, leading to their inclusion on the Birds of Conservation Concern Red List. Declines are greater in urban than in rural areas, and in eastern and south-eastern Britain than in other parts of the country (where the population is stable or increasing). A new study by the BTO has used data collected by volunteers participating in Garden Birdwatch (GBW), the Nest Record Scheme (NRS) and the Breeding Bird Survey (BBS) to investigate possible reasons underpinning these 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.
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