canberrabirds

Estimating numbers

To: "'John Brannan'" <>
Subject: Estimating numbers
From: "Geoffrey Dabb" <>
Date: Thu, 18 Mar 2010 15:49:47 +1100

Thanks John.  It's not easy and it's one of those things where if you don't have any measure of your estimates you don't get any better.  I'm sure that the experts mentioned by Dan learnt from the experienced estimates of others.  Photos might have helped.

 

I'm not too good myself and I won't go on and on, but here are exactly 100 waders:

 

100 waders.JPG

 

-----Original Message-----
From: John Brannan [
Sent: Thursday, 18 March 2010 2:36 PM
To: Geoffrey Dabb
Cc:
Subject: Estimating numbers

 

Geoffrey,

 

Thank you very much for this. It was highly instructive. My own hesitant

initial estimate was 60-70 birds - serious undercounting, as it turns out.

In future, I wonder whether it might be helpful if, when counting

smaller numbers (20 or so) where counting of individuals is feasible,

one were to take a step back after the count, take a fresh look at the

group and say to oneself, "Right. That's what 20 birds looks like."

 

John Brannan

 

Geoffrey Dabb wrote:

> 

> Very interesting.  Estimates mentioned to me ranged from a wary ‘0 –

> not starlings’ to ‘200-300’.  It might or might not be helpful if I

> told you that each of the first 4 coloured sections represents 50 birds:

> 

> 

> 

> I would think that very few people would know, intuitively, what 200

> birds ‘looks like’.  Barbara P mentioned the semi-counting method of

> counting 10  -  then counting the number of tens.  That depends on

> having the flock in view for long enough.  John Rawsthorne – an old

> sheep-counter like a few others – said if it looks like 100 it’s

> probably twice that number.  That is, in  a way, knowing what 200

> ‘looks like’  -  it looks like 100.  That kind of knowledge comes from

> knowing at some stage the actual number of estimated quantities, so

> perhaps the sheep counters have an advantage.

> 

> 

 

 

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