Roger-
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 http://www.rosssilcock.com/PSPYPE.jpg and http://www.rosssilcock.com/PSPYPE2.jpg.
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 http://www.rosssilcock.com/PSCOPE2.jpg doesn’t seem to.
Ross
Ross Silcock P.O. Box 57 Tabor, IA 51653 New Zealand Land and Pelagic Bird Tours http://www.rosssilcock.com
