help required to identify races of Sooty Oystercatcher

To: <>
Subject: help required to identify races of Sooty Oystercatcher
From: "Peter Menkhorst" <>
Date: Tue, 29 Jan 2008 21:37:57 +1100
I think that you have slightly unreasonable expectations in expecting to be 
able to determine the subspecies of Sooty Oystercatcher at any one place. It is 
precisely because you are dealing with subspecies that identification of an 
individual bird can be difficult. Subspecies, by definition, interbreed, and 
therefore intergrade. That is, you should expect morphologically intermediate 
forms and individuals. If the two taxa did not interbreed they would be 
separate species and one could expect that they would have diverged to some 
extent and that such divergence will be reflected morphologically, meaning that 
reliable diagnostic features will exist. For subspecies, this does not apply - 
geographic and morphological boundaries are fuzzy and there will always be 
identification questions that are unanswerable without taking a representative 
sample of the population.

Because of this problem our knowledge of the distribution of subspecies is 
often rudimentary. That is why I consider the ticking of subspecies to be a bit 
sus, with some obvious exceptions where morphological divergence is obvious - 
but you still get intermediate individuals where the two forms interbreed.

But thanks for posting your photos - they are very useful to field guide 


Peter Menkhorst

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