Re: Pied Oystercatchers on Lord Howe and Norfolk Islands

Subject: Re: Pied Oystercatchers on Lord Howe and Norfolk Islands
From: David James <>
Date: Mon, 06 Apr 1998 16:56:13 +1000
Richard,  Mike, et al., 

When dealing with Vagrants an important rule is that normal distribution of
the species is irrelevent, or at least unreliable, circumstantial evidence.  

Species biology rather than proximity is more important. Take for instance
the rare Buff-breasted Sandpiper that turns up all over the world, compared
with the super abundant Dunlin. Hanzab records PIOY to make limited medium
movement across Bass Strait and posssibly across Torres Strait. SIPO make
more regular medium distance migrations between South I and North I. But
this is also circumstantial evidence. 

HANZAB is an authoritive volume, but that does not guarantee that it is
always right. In particular, it is outside the scope of the DISTRIBUTION
AND POPULATION section of HANZAB to vet records, it merely reports records
from the literature and from the Rarities Committee files. Often records
are reported as unconfirmed, however, in the case of Oystercatchers this is
not so (I suspect that the significance of the situatuion was not realised
at the time the texts were prepared). There are records in HANZAB of b&w
Oystercatchers from the Kermedecs, Chathams, Norfolk and Lord Howe. The
first two locality records are attributed to SIPO and the latter two to PI
Oyc, probably because they were reported in the primary literature by
Australian and NZ observers respectively. They could refer to SIPO, Pied
Oyc , Variable Oyc, Eurasian Oyc, Chatham Oyc, American Oyc or even
Megallanic Oyc. The only evidence that helps is photos, field notes or
specimens. When preparing Oystercatcher plumage texts for HANZAB a few
years ago I did not find any speciemens, photos or descriptions from any of
these islands that would allow positive identification (though some could
exist). (I was also surprised at how poorly the identification NZ
Oystercatchers is known). If people do not take and circulate detailed
descriptions of vagrants their identity will never be known. Descriptions
need to include diagnostic information, and Oycs are a very very difficult
group of birds (whether b&w or just black), as some Brisbane observers of a
possible variable Oyc learnt the hard way last summer. HANZAB contains some
info, as does "Shorebirds" by Hayman et al. But this is a frontier area for
identification that has received little attention because of the perceived
allopatry of the species in the 2 complexes. Perhaps Eurasian Oyc occurs
annualy in Australia. 

Perhaps some oystercatchers will be identified on Pacidfic islands in the
future, but those that have occured to date will remain Haematopus sp.
unless there are some better notes or photos around. Regardless of this,
Oystercatchers will always be a difficult group to identify. 

David James
PO BOX 5225
Townsville Mail Centre 4810

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