House Sparrows approach six-year high
BTO Garden BirdWatchers are seeing more House Sparrows in their gardens. Numbers are approaching a six-year high following a big drop that occurred in the middle of last decade, especially in 2006 and 2007. This drop coincided with an outbreak of the disease trichomonosis, which caused the death of many Greenfinches and Chaffinches. At the time, a number of House Sparrow casualties due to this disease were logged and so it is possible that this species was affected more widely than at first we had realised. Formal analyses need to be conducted in order to investigate this possibility further. Since 2008 a noticeable, steady upturn in GBW counts has been recorded (see graph right).
With large numbers of GBW sites in England, Scotland and Wales, comparison of how House Sparrows are doing in these countries is possible. The graph below shows average weekly counts of House Sparrows in GBW gardens from January to mid-June in each year (data have been restricted to these months so that data from 2012 are comparable with previous years). One of the most obvious features is that counts of House Sparrows in Scottish and, particularly, Welsh gardens are typically higher than those in English ones. Over the longer-term, declines of House Sparrows have been steepest in urban habitats, and since human population densities are greater in England than in Scotland or Wales, this might contribute to fewer House Sparrows being seen in English gardens. Within England, House Sparrows are now seen least often in gardens in the south east and in Greater London – again where human population density is very high.
The recent recovery in numbers of House Sparrows in gardens has followed slightly different trajectories in these three countries. The graph left shows how numbers in English gardens were at their lowest in 2009 and have risen progressively since. In Wales, the lowest point was in 2010 and has been followed by a more pronounced recovery than in England, with numbers now approaching a seven-year high. Counts in Scottish gardens reached their lowest point in 2008, rose markedly in 2010 and 2011 (even eclipsing Wales during these years) but have dropped back slightly in the first half of 2012. During a typical week so far this year, an English garden has hosted 4.6 House Sparrows, a Scottish garden 5.0, and a Welsh garden 6.5.
Tell us what you see!
If you do not take part already, please tell us about House Sparrows and other birds in your garden by getting involved in Garden BirdWatch. For a free enquiry pack, including a copy of our quarterly magazine Bird Table, please email gbw [at] bto.org.
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