Pycroft's Petrel for Australia?

To: "Roger McNeill" <>, <>
Subject: Pycroft's Petrel for Australia?
From: "Ross Silcock" <>
Date: Tue, 28 Dec 2010 01:29:43 -0600

There are 2 excellent photos of Pycroft's Petrel on my website, taken in NZ off Whitianga by Phil Swanson in Nov 2009. These can be found at and

I agree with the sliding scale between Cook's and Pycroft's. The Lord Howe bird is towards the Pycroft's end but I wonder about the extent of white above the eye and on the forecrown (many Pycroft's seem to have a clearer demarcation between the dark and light in this area). Also, the dark patch below the eye in Pycroft's tends not to separate obviously from the surrounding dark area; the Lord Howe bird has a fairly distinguishable dark eye patch, but possibly due to the lighting conditions.

Having said that, though, I'm not sure Pycroft's can be ruled out. Your point about the longer central rectrices is interesting- the 2 Pycroft's pics above show a "pointier" tail, whereas this Cook's doesn't seem to.


Ross Silcock
P.O. Box 57
Tabor, IA 51653
New Zealand Land and Pelagic Bird Tours
-----Original Message----- From: Roger McNeill
Sent: Monday, December 27, 2010 11:18 PM
Subject: Pycroft's Petrel for Australia?


Back in Oct a Jack Shick took a photo of a cookilara taken off Lord Howe on the way to Ball’s Pyramid. At the time he thought it might have been a Gould’s. I was sent a copy by a friend who thought it may be something else...I believe it
to be a Pycroft’s.
While living in NZ I spent a fair bit of time trying to suss out the differences between Cook’s and Pycroft’s and this bird is a very strong candidate for the latter. I have seen about a hundred Pycroft’s and many hundred Cooks and it has all the indicative features that I am familiar with for Pycroft. There are many that say these two species can’t be separated at sea but I believe that there is a bit of sliding scale with individuals on the far end being distinctive and not
too difficult to separate.
Because this would be a significant record for AU let me toss it into the public forum for debate. I am in no way an expert but a few mates and I came up with
some rules of thumb that were good ways to separate the two.  Of these, the
features which stand out to me are:
1.       Strong dark grey hood and distinct eye-line
2.       Deep, thick and distinct mark under the eye which is greater behind
than in front of the eye
3.       Unbroken underwing carpal bar
4. And most distinctive which I have never seen published anywhere is a
slight extension of the central tail feathers on Pycroft’s vs Cooks.
I have asked Tom Tarrant to post this for me at the Australasian Bird Image Data
Base.  Please find the image at the following link:

Roger McNeill
Samford Valley, SEQ

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