As usual Frank O'Connor has raised some interesting points that lead me to
make several comments:
Frank wrote
>Having done pelagic trips in a number of states, what surprises me is how
>seabird species seem to behave differently in different states.
The boat itself is a major factor in the way seabirds respond. Having said
that:
>Wedge-tailed Shearwaters seemed to flock in big numbers behind the boat off
>Wollongong. Yet off Perth, they fly around but have seldom landed behind
>the boat.
Off the coast from Geraldton WTSW behaviour reminded me of the birds at
Wollongong. Notably excepted were the 'pale morph' birds, which were more
interested in the horizon than our boat!
>Perhaps the larger Flesh-footed Shearwaters cause them to stay
>away, although I have never seen interaction between the two species. At
>Lord Howe Island, we had Wedge-tailed Shearwaters and Flesh-footed
>Shearwaters together close to the boat. The Wedge-tailed Shearwaters breed
>on Rottnest Island, while the Flesh-footed Shearwaters don't breed close to
>Perth, so this might be another factor?
On the east coast relative numbers are the key in this interaction. WTSW
usually outnumber FFSW significantly and happily scrap life out. Once FFSW
numbers start to appraoch those of WTSW, which is unusual, the balance of
power seems to shift towards FFSW. Large numbers (>50) of Pomarine
Jeagers also cause the WTSW to abondon ship following for obvious reasons.
We also experience days whem WTSW show no interest in the boat for no
reason apparent to us.
>Great-winged Petrels landed readily close behind the boat off
>Wollongong. They are fairly common on the Perth pelagics but very very few
>have landed on the water, and never close to the boat.
The Great-winged Petrels that occur for most of the year on the east coast
are P. macroptera gouldi (NZ breeders) and as Frank observes often attend
fishing vessels closely. In the winter months the nominate P. m.
macrpotera occurs in much smaller numbers in the Tasman Sea and are boat
shy to the point that we have had to respond tactically to identify them.
I presume that the birds observed offshore from Perth are the latter so in
fact there is not a behavioural difference. Any comments from VIC or TAS
where both would occur?
>We get Soft-plumaged Petrels in quite large numbers (up to 70) on the
>winter trips off Perth. They are a certainty on trips from June to mid
>September. While only one or two have landed close to the boat, we usually
>get several flying around close to the boat for a period of time.
Sounds wonderful Frank!
Dr P.J. Milburn
Biomolecular Resource Facility
Australian National University
GPO Box 334
Canberra
ACT 0200
+61 2 6125 4173 'Phone
+61 2 6125 4326 FAX
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