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Hi Birders,
Being a numbers man i could not resist
giving some input re local bird lists.
For about 25 years i have been recording birds at
North Lake and Blue Gum Lake near Perth.
At North Lake the total is 104 and Blue Gum is 72.
The highest daily counts have been 55 at North Lake in Jan. and Feb. and
38 for Blue Gum Lake in Feb.
This is expected due to the summer migrants and the
westwards pull to the coast as the inland lakes dry out.
The interesting relationship is that the total
number of species is almost twice(sorry to get into accountant speak but both
ratios are1.89 ) the highest individual count conducted when it is likely
the max. numbers could be expected.
This rule of thumb could prove very useful when
time ( such as 25 years! ) does not allow a very long and exhaustive
survey to determine the total numbers of species. It is of course based on surveying the same area over and over
and on a relatively small area based around a Lake.
I would be interested to see if this ratio is
consistent with other surveys as it could be used for conservation and
other reasons to estimate the total number of species based on only a few
visits.
Regards
Wynton
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