Size of Great Crested Grebe

[Steve Read <>]

Martin – I described this Great Crested Grebe as “Slimmer than accompanying coots” in an eBird posting this morning (http://ebird.org/ebird/view/checklist/S36188855), which avoided consideration of the largest dimension. It certainly looks finer and more elegant than any gallinule. I presume that it’s a young bird?

 

Steve

 

From: Martin Butterfield [
Sent: Sunday, 23 April 2017 3:02 PM
To: COG List <>
Subject: [canberrabirds] Size of Great Crested Grebe

 

In an ebird posting about the Yerrabi Pond Great Crested Grebe a comment is made, supported by evidence in a photo, that the Grebe is slightly smaller than a nearby Eurasian Coot.  This surprised me more than somewhat as I had thought the Grebe to be much larger.

 

Consulting the overall measurements given in Pizzey and Knight this would seem to be the case.   The Grebe ranges from 48-61cm in overall length (averaging these gives 54cm) while the Coot is 35-38cm (37cm).  

 

On looking more closely at the checklist photo it seemed that it was the Coot's torso which seemed larger than that of the Grebe.  To check this out I measured the proportions of body parts of the two species as depicted in the Field Guide and scaled them up to the average lengths cited above.  The torso of the Grebe came out to 25.8cm while the Coot came in at 23.1cm (roughly 10% smaller).  

 

If however one takes the smallest length quoted for the Grebe and the longest length given for the Coot one gets 22.9cm for the torso of the  Grebe and 23 .8 (~5% larger) for the Coot.  

 

So it would appear that the Grebe is a small specimen while the Coot has clearly propered on whatever its been finding to eat in the Pond!

 

Martin Butterfield

http://franmart.blogspot.com.au/

 

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