South Island Oystercatcher Haematopus finschi

in Sydney Harbour, NSW 1st of March, 2015

Joshua Bergmark, with Ashwin Rudder and Nathan Ruser, Biggles Csolander, David Stowe, Rob Hynson and Paul Johstone

joshua.birdmark@gmail.com - JB

noisypitta@gmail.com - AR

nrg800@gmail.com - NR

Summary

A South Island Oystercatcher was seen and photographed by Biggles Csolander (BH) on the 1/03/15.

Initially the bird was identified as a strange Australian Pied Oystercatcher (OZPO), but viewing of photos

on Facebook that night by Joshua Bergmark (JB), Nathan Ruser (NR) and Ashwin Rudder (AR) amongst

others resulted in unanimous identification as a South Island Oystercatcher (SIPO). If accepted by BARC,

this would be Australias 10th record, the most recent being from January 2015 in northern NSW.

Introduction

BC regularly guides tours to Shark Island, and on the 1st of March photographed an

oystercatcher, which he noted as unusual for the harbour, with some strange proportions.

Photos were uploaded to Facebook where JB recognised the bird immediately as a

potential South Island Oystercatcher. After a general agreement from other birders online,

JB and NR arrived with other birders on the first ferry to Shark Island the following day,

and relocated the bird, obtaining views to within a few metres and excellent photographs

showing all the diagnostic features characteristic of the species. The bird was flushed by

an inconsiderate twitcher mid-morning and not seen for the rest of the day until, on the

return boat trip, it was located on a rock just offshore from the Chowder Bay Headland at

-33.843925,151.254304. The bird spent the next month visiting Shark Island, Chowder

Bay and Balmoral Beach at various intervals dependent on the tides, and was ticked up

by many birders. A pelagic out of Rose Bay on the 11th of April located three

oystercatchers on Shark Island in the same view Sooty, SIPO and OZPO. The last

confirmed sighting was on the 21st of April, 2015, by David Mitford at Rose Bay.

Description

The bird was initially noticed by JB from photos to have a significantly longer bill than OZPO, along with prominent white bars visible on the folded wings. The initial photos from BC didnt strictly show all the clinching ID features, so the following day JB, AR, NR, and others set out to relocate the bird. The obliging oystercatcher was soon found, and observed by many over the next few weeks, with hundreds of photos being obtained. Attached shots show all relevant ID features for species separation.

White underwing and triangular rump with trailing wing edges Paul Johnstone

Relatively long bill compared to OZPO, speckled breast demarcation and white bar visible on folded wing. Additionally, the white hook in front of the wing is a key ID pointer, although not a distinguishing feature in itself David Stowe

Relatively short, stubby legs compared to OZPO David Stowe

Trailing edge in flight reaching body, and triangular white rump Rob Hynson

Original photos from 01/03/15 showing various features and locality Biggles Csolander

Species Separation

1: Australian Pied Oystercatcher (Haematopus longirostris) The most likely pied-type oystercatcher on the east Australian coastline, and very similar to SIPO, however since confusion between these two species is a regular occurrence, relevant ID features are well recognised. An OZPO would have a shorter, stubbier bill, with no white wing bar extending to the body from the wings, and no white triangular rump extending onto the back. Legs are also proportionally longer on OZPO, though more difficult to observe in individual birds with no comparisons.

Further, the bird in question shows all relevant features perfectly, with no deviation from the norm, so hybridisation is also ruled out beyond reasonable doubt. This had occurred with the north NSW bird earlier in 2015, where a second individual confused many twitchers, until eventually the two-bird theory was applied, with one suspicion being that a long-staying pure SIPO had bred with an OZPO to produce the hybrid, confusing offspring.

2: Variable Oystercatcher (Haematopus unicolor) Only the completely pied form of Variable Oystercatcher is similar to SIPO, however it differs in possessing an altered bill structure observable in the linked photograph below, with the SIPO bill (centre) clearly more elongated, upcurved, and tapered to a point than the two adjacent Variables: http://bit.ly/1FqwDJu Variables also usually lack to white tab in front of the wings, which is clearly visible in all photos of the Sydney SIPO above. It is also worthy of note that Variables very rarely, if ever, have a completely pied phase, as almost all birds in New Zealand have very obvious speckling or black smudges on the chest border, wing bar and rump.

3: Eurasian Oystercatcher (Haematopus ostralegus) An individual of this species occurring in Australian territory would be a phenomenal occurrence, however brief notes are included here for completeness. This species typically has a down-curved, and much shorter bill than presented in the above photographs, with a more evident white wing bar at rest, and a sharper, less splotchy breast demarcation. Note that some authorities consider SIPO conspecific with Eurasian Oystercatcher.

Previous Reports

SIPO have been reported numerous times in Australian Territory, however not all have been submitted to BARC. The most recent verified report was from Victoria Point, Qld 2011 (Accepted), while the Tuckers Rocks bird, NSW 2015 has not been processed as of yet (Under Review).

Acknowledgements

Special thanks to Biggles Csolander for finding the bird, and to those who supplied photos for the report - David Stowe, Brian Johnstone and Rob Hynson. ID notes taken from Heather and Robinson, Field Guide to the Birds of NZ, Handbook of the Birds of the World, and JBs field experience with all Australasian oystercatchers.