canberrabirds

Estimating numbers

To: Geoffrey Dabb <>
Subject: Estimating numbers
From: John Brannan <>
Date: Thu, 18 Mar 2010 14:36:05 +1100
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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