Knots and Petrels

To: "Trevor Ford" <>
Subject: Knots and Petrels
From: <>
Date: Mon, 19 Oct 2009 21:30:32 +1100
Hi Trevor,
I'd consider the undertail to refer to the underside of the rectrices (the actual tail feathers). They are dark in Soft-plumaged Petrel. In contrast, the undertail coverts which are the smaller more flexible feathers that sit below the rectrices and extend to the rear of the vent are white in Soft-plumaged Petrel. When Onley and Scofield state 'white undertail' they more accurately mean white undertail coverts. O&S may have justified the use of 'undertail' as a more general term somewhere in a terminology section as most tubenoses show fairly long undertail coverts that obscure the underside of the rectrices (undertail) - it might have been a good way to save a few words in most species accounts.

Here is a pic of a Soft-plumaged petrel that shows the dark undertail and the contrasting white undertail coverts.


Rohan Clarke

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