At 15:28 30/09/2020, John Bibby wrote:
>... However, the point of the article is the methodological point
>that sampling needs to take account of cyclicities. The most likely
>reason for "fewer butterflies" is not (shock, horror!) that there
>are fewer butterflies, but that this year, because of the good
>weather, they came out earlier..... However, the shock-horror story
>makes better headlines. ... It's like systematic sampling when there
>are perioducities in the sampling frame - not a good idea!
I don't disagree with any of that. However, in relation to the side
issue (small birds) I introduced, there's not really any sampling
involved - it is essentially a (local) 'census' of all the small
birds in my garden each year. For the last 30+ years, there have
been countless of them, on almost every day of the year, but this
year there have been virtually none. Others in the neighbourhood
report a similar experience this year.
Assuming that it is a genuine ('local') phenomenon, the nearest to an
explanation I can think of is the red kites. However, their numbers
have been increasing gradually for well over a decade, so I don't
really understand why it should have so suddenly had such a dramatic
effect on the small birds.
Kind Regards,
John
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Dr John Whittington, Voice: +44 (0) 1296 730225
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Buckingham MK18 4EL, UK
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