Mike Carter, birder of note, twitcher, seabirder and sometime desert
dueller, has posed an interesting question: Are the pied oystercatchers
seen occasionally on Lord Howe and Norfolk Islands Pied Oystercatchers
(Haematopus longirostris), South Island Pied Oystercatchers (H. finschi) or
both?
I have more than a passing interest having seen a pied oystercatcher on a
visit to Lord Howe Is in Nov 96. Unfortunately I was sufficiently dozey at
the time not to have treated the sighting with anything but the mildest of
interest. I neither realised that such sightings are very infrequent nor
that it might be either of these two very similar species (I therefore made
no attempt to identify it to species, assuming it was an Australian origin
Pied Oystercatcher).
I note that Ken Simpson in the island lists at the back of his field guide
lists Pied Oystercatcher as a vagrant to LHI and SIPO as a vagrant to NI.
HANZAB (assumed to be the current authority?) notes single vagrant PO's on
LHI in 1950 and 1982, and vagrant PO's on NI in 1960 (x30), 1970 (x2) and
1983 (single).
With regard to SIPO's HANZAB states: "Vagrant black-and-white
oystercatchers on Norfolk and Lord Howe Is have been attributed to this
species but not acceptably confirmed and are considered further under Pied
Oystercatcher (qv)."
As I understand Mike Carter's argument (and I can't purport to have heard it
fully expounded) New Zealand's closer proximity to NI (772 kms cf 1367 kms
from Australia) and the SIPO's known propensity for flocking and migrating
make it the more likely vagrant to Norfolk Is and should have caused HANZAB
to take a stronger position regarding the likelihood of the Norfolk Is birds
being SIPO's rather than PO's.
I assume that the opposite proximity issue for LHI (570 kms from Australia
cf 1350 kms from NZ) and perhaps the records of only single birds outweigh
the rather limited migratory behaviour in PO's and make this the more likely
species on LHI.
Anyone feel like making a contribution? (I will send all contributions on
to Mike Carter for his interest/edification - in hard copy since he is not
"on-line".)
Richard Nowotny
From: Dr Richard Nowotny
Melbourne, Australia
Tel. (w) 61-3-9214.1420
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