On 05/11/2010 14:24, Janet wrote:
In article601b0ad9-3cc3-464d-8496-dbcb7987be30
@e20g2000vbn.googlegroups.com, says...
All sounds a bit random and uncontrolled to me.
:-) AIUI, statisticians arrange randomisation and anonymity, to avoid
biased results.
That is actually difficult to do with a self seleted "random" sample. By
definition anyone prepared to watch and count for an hour is at least
slightly interested in wildlife and birds in particular.
This means that the folk who have tarmaced their entire front garden for
carparking and installed CCA treated lumber decking on the rest will be
under represented in the sample.
I don't see how they
can tell anything about numbers. Distribution, maybe. Depending on
how accurately people identify the birds.
For anyone unsure of bird ID, there are free photo leaflets available
on request; a good way to encourage children to learn how to recognise
birds. I would guess most adult participants are sufficiently interested
in birds to recognise their local species.
Bird-counts help map population distribution changes. We've been
doing gardenbird counts and local sighting-reports for years. I'm not a
member of any of the bodies I return bird counts and sightings to; there
is no financial or reward incentive involved.
I reckon it is fairly harmless and as you say helps get some more people
interested in birds and wildlife.
Regards,
Martin Brown