Sunday, August 24, 2008

not fast enough...

Bird responses to climate change are being monitored and measured in different ways e.g. early arrival dates, late leaving dates and increased frequency of vagrants. Another way is by monitoring increasing ‘range’ – summer migrants moving further north and winter migrants coming less south. One event that has been missed, till now, is how much of the species population has ‘shifted’ within an already existing range. Ornithologists in France have now attempted to answer this question.

Using the French equivalent of the BBS, together with European climate data to calculate species /community temperature indexes, they have been able to calculate a 91km northward shift in bird community composition - meaning that the bulk of the bird community has moved, on average, 91km further north; and that much of this movement is still within their known range.
Using the same modelling process they have shown, during the same time frame, that the equivalent temperature increase has moved northward by 273km – meaning that bird responses to climate change are failing to keep pace.
These results suggest that birds are experiencing greater change within their range than at their (range) margins. If this is the case then it is far more important to monitor the birds in our back gardens than ever before – much like sparrows and starlings if we don’t, the change may be realised long after it is already too late.

Ref: Proc.R.Soc.B doi:10.1098/rspb.2008.0878 (published on-line).

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