Bird Numbers

To: <>
Subject: Bird Numbers
From: "Wynton" <>
Date: Fri, 25 May 2001 22:05:03 +0800
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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