Hi,
On Saturday 23rd the Christchurch branch of OSNZ had a field trip to
Lake Ellesmere.
On the lake fringe at the end of Wolfes Road there were 2 all dark
oystercatchers. As variables are very unusual at this site and this
habitat (reed fringed mud) they were looked at in more detail than
typical for this species.
Both birds had tails that projected beyond the wing tip. Both
Shorebirds and Handbook of the Birds of the World state that this is
the only feature that distinguishes sooty oystercatcher from the black
phase of variable. A visit on Sunday evening allowed me to note that
on at least one of the birds the wing feathers were very fresh
(revealed during a wing stretch); therefore, the projection of the
tail beyond the wing was a real feature and not caused by a shortened
wing as the result of abrassion to the wing tip.
The length of tail projection was estimated as 4/5th of the distance
between the bill base and the start of the eye. It matches perfectly
the plate in the Handbook of the Birds of the World. Whilst I have not
yet been able to access volume 2 of the Australasian Handbook it
appears that the birds are sooty oystercatchers. If so, this would be
the first proven record for NZ - although Collin Hill photographed a
probable bird a few years ago.
The birds are immatures with dull legs, darkish tip to the bill and a
brownish cast to the body feathers that is slightly more noticeable on
the upperparts - compared to the underparts.
Does anybody know the extent of tail projection demonstrated by sooty
oystercatchers or if variables can ever show tail projection?
Would it be necessary to catch a bird and take biometrics to be
certain of the identification?
Cheers
Karl
-----------------------------------------------------
Dr Karl Evans
PO Box 84
Ecology & Entomology Group
Lincoln University
Canterbury, NZ
Tel: (03) 325 2811 ext. 8174
Fax: (03) 325 3844
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