For my personal bird records I use a system that could provide some of the
information required, i.e. the likelihood of seeing a particular species in
a particular spot. Rather than just recording what birds I've seen where, I
record the date I first saw the bird there and subtract one less than the
date that I arrived. So if I saw the bird on the first day, it gets a score
of 1. Over a long enough time, or a large enough number of visits by
birders, the data can be averaged out to provide an approximation of
probability data. For my home list, where I am present most days, the data
is now large enough to give fairly good approximations of the likelihood of
seeing any species. For any species not seen in the month, I give a score of
32. Thus, if the bird is never seen, it will have an average score over time
of 32. If it is a rare vagrant, seen once, it will end up with a score of 31
point something. Magpies etc. that are seen nearly every day, end up with a
score close to 1. Once the number of observation days is high enough the
data can be subdivided and averaged such as to give a likelihood for any
month of the year, so migrants will have a high score in June and a low one
in November. At the moment, my personal data is only extensive enough to
give reliable likelihood estimates for places I vist (or have visited)
often. If all birders took up my system, I think it would go a long way to
providing the sort of information that the originator of this thread wanted.
Paul Osborn
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www.birding-aus.org
birding-aus.blogspot.com
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