The number of rarite reports accepted by BARC (n) = x - a - b - c - d
where
x is the number of rarites that actually visit Australia
x - a is the number that people perceive [see or hear], in many cases
without consciously being aware of the birds
x - a - b is the number that people observe [they are aware of the
birds]
x - a - b - c is the number that people correctly identify
x - a - b - c - d is the number of correctly identified birds that are
reported to BARC with sufficient detail to become an accepted sighting
The question is whether x is greater than 1% of n. Rarites that turn
up to twitcher hotspots - eg WTP, BBO, Penrice, Ash Island, Buckley's
Hole have a high probability of being observed and identified. Rarites
that turn up in areas not on the twitching map - eg Burren Junction are
generally not observed.
The reason more rarites are being reported is that more twitchers have
telephoto lenses and are reporting sightings on Birding-Aus etc - the
following article provides a picture of the situation in the UK this
year ...
Regards, Laurie.
http://environment.independent.co.uk/nature/article3255703.ece
A very British bird boom
This year more rare birds have been sighted on our shores than ever
before. And, as David Randall finds, it's our very own hi-tech
twitchers that we need to thank
Published: 16 December 2007
< snip>
The interesting thing is that the "bird of the year" came and went
without being seen by a twitcher - an exhausted Yellow-nosed Albatross
turned up in someone's yard, was taken to a rescue centre, photographed
and released the next day ...
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