Hi all,
I recently found the following picture on the internet of a Gould's Petrel
photographed off the Gold Coast on 16/3/2002, see
www.indiabirds.com/obc/Content/ImagePage.asp?Bird_ID=1148&Bird_Family_ID=123
--- or go to --- www.indiabirds.com/obc/Default.asp and search for
Pterodroma leucoptera or Gould's Petrel.
Once I saw this picture the underwing pattern immediately stuck out as
unusual. I have seen many underwings of Gould's Petrel (all on land) and
none have been as pictured in the photographed bird. The amount of blackish
colouration on the coverts is much more extensive than what I am used to,
and approaches that of Black-Winged or Mottled Petrel.
I am not disputing the identity of this individual, the extensive dark cap
over the head and nape, extending in a relatively straight line from the
suborbital patch to the side of the breast which is similarly dark, is
diagnostic for P. leucoptera and P. brevipes. However, P. brevipes can be
easily ruled out because of the colouring of the underside of the remiges.
According to Hanzab the areas on the underwing of P. leucoptera are
described as such:
Greater Primary Coverts - all white, except outer web of outer covert which
is brown-grey.
Median Primary Coverts - all white, except outer covert and outer web of
next innermost (dark-brown).
Marginal Primary Coverts - outermost coverts dark brown tipped white, rest
white.
Carpal Joint - marginal, lesser and basal halves of median coverts dark
brown.
Innerwing - from carpal joint diagonal bar extends three-quarters the length
of the radius-ulna towards the body with distal halves of median coverts and
narrow fringes of marginal coverts white. Rest of coverts white.
I find the description of the innerwing a little confusing, there is no
mention of lesser underwing coverts specifically, yet the claim is made that
the rest of the coverts are white which would include the lesser coverts
according to how this is written. Yet, the lesser coverts do form the
diagonal bar, and from my inspection of the underwing of this species it is
the median and lesser coverts that form the diagonal bar once it begins to
thin out from the carpal joint, yet the coverts are not wholly dark (i.e.
either have white bases - lesser, or white distal halves - median).
Anyway, getting to the point (concise writing is not my forte) the
photographed bird does not conform to this description. It appears that all
marginal and median primary coverts are dark brown, the greater coverts
remaining white. On the innerwing the diagonal bar appears much thicker with
perhaps all of the lesser coverts being dark and most of the median coverts
(but this is very difficult to tell from the photo). Suffice to say that the
underwing has much more dark colouration than is typical of Gould's.
In case anyone is wondering if the discrepancy could be attributed to the
bird being a New Caledonian Petrel P. l. caledonica, especially given the
bird was observed off SE QLD, then according to Hanzab the diagonal bar on
nominate leucoptera is slightly heavier than in caledonica.
I welcome comments from seabirders experienced with Pterodroma petrels,
particularly those who have seen Gould's at sea. What possible implications
does this have for identification of Pterodroma petrels using the underwing
pattern as a significant field ID feature?
One LAST thing - if you have come this far you are obviously interested in
seabirds, so this Saturday (20th March) the Australian Bird Study
Association in conjunction with SOSSA is hosting a Scientific Day entitled
"The Tasman: a bird's sea" with lots of interesting talks on seabirds, this
is to be held at Macquarie University. See www.absa.asn.au/comingevents.html
for details. You can register on the day at the venue. Hope to see you
there!
Cheers, Dean
_________________________________________________________________
Find love today with ninemsn personals. Click here:
http://ninemsn.match.com
--------------------------------------------
Birding-Aus is now on the Web at
www.birding-aus.org
--------------------------------------------
To unsubscribe from this mailing list, send the message 'unsubscribe
birding-aus' (no quotes, no Subject line)
to
|
