Sparrows

["martin butterfield" <>]

Much of the analysis of the GBS is in terms of the A value, possibly reflecting the fact that it is available.  However Geoffrey's message below has caused me to look the series of F values for House Sparrow and Common Starling.  A couple of graphics are attached (and I have checked that the file size is <100Kb). 

 

The patterns for the two species are rather similar. When looking at the entire series - especially when summarised through a trendline (which fits the data quite well as shown by the correlation coefficients) - it appears that the serious decline in the values of F for both species starts around year 15 (in real money, 1995-96). 

 

Thus I created the second graph restricted to the period since that year.  Again the trendlines for both series are similar and fit the data well.  I will leave it to others to offer reasons for the upwards 'flick' at the end of the trendlines but suggest that the impact of the year 27 data for these species could be quite interesting!

 

Martin

On Tue, Mar 4, 2008 at 10:18 AM, Geoffrey Dabb <> wrote:

This takes us to the heart of COGland, and into the territory of Philip and Martin.  Below is a slide from my off-the-shelf talk on Canberra birds.   The percentages refer to SITES where the species has been recorded at all in a full year (not abundance).  The first column is derived from Philip's analysis of the first 21 GBS years, treating those years as a block.  Then, sparrow and starling were firmly entrenched in the Top Ten GBS birds.  In the more recent 2 years shown, the sparrow was not recorded at all in 20% of the (3-hectare) sites.   I need to update the graphic, but the trend continues.  Martin tells me that in 06-07 only 78.6% of sites had sparrows.   Given that that is over a full year, it also suggests that they don't move around much.   

 

080304 Sparrow and starling.doc
Description: MS-Word document

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