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Old Friday 1st July 2005, 01:55   #1
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Black-bellied vs White-bellied Storm-Petrel

Anyone familiar with these species...?

In HBW vol. 1 the authors note that the legs of Black-bellied Storm-Petrel Fregetta tropica extend beyond the tips of the tail in flight. Is this also the case in White-bellied Storm-Petrel Fregetta grallaria, or can this be a feature to distinguish between the two?

Also, the few sources I have at hand referring to these species note that the black central stripe on the belly of F. tropica is variable - does it ever vary to the point of hardly being visible?

Thanks in advance for any help you can provide.

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Old Friday 1st July 2005, 19:26   #2
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I have no experience of either. Just in case you haven't got a copy, Harrison suggests that the variation in underpart colouration has been over estimated , though I am guessing HBW is a more recent publicaton. He states also that beyond plumage, the only reliable sturctural disciminator is a combination of tarsus, middle toe and wing length.

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Old Friday 1st July 2005, 21:10   #3
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I don't have that reference Jane, but it was published after HBW vol. 1

The few drawings of the F. tropica i have found show pretty solid amounts of black below. I'll go to the university library on monday and see if they have a copy of Harrison.

Many thanks

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