birding-aus
Danny Rogers recently asked whether YTBC farm wood-boring insect larvae. At
the suggestion of a colleague, I passed the query onto Rob Floyd at CSIRO
Entomology and he has kindly provided the following feedback.
Regards
Michael Atzeni
Intensive Livestock Environmental Management Services
Department of Primary Industries
PO Box 102 (203 Tor St)
Toowoomba QLD 4350
AUSTRALIA
Phone +61 7 4688 1318 Fax +61 7 4688 1192
Email:
> -----Original Message-----
> From: Rob Floyd [SMTP:
> Sent: Tuesday, 9 March 1999 23:03
> To: 'Atzeni, Michael'
> Subject: RE: birding-aus Yellowtail Black Cockatoos
>
> Dear Michael,
>
> Greetings - after many years of not seeing each other.
>
> Black Cockatoos are well known for their behaviour of extracting insect
> larvae from living trees and causing serious damage in eucalypt
> plantations.
> This has been recorded in the literature from the north coast of NSW and
> was
> one factor which led to a forestry company moving away from plantation
> grown
> eucalypts on ex-farm sites in that area. Cockatoos often extract larvae of
> the wood moth family (Cossidae) which can be rather large and make tunnels
> in excess of 2 cm in diameter in the trunk of trees. They also have been
> observed to remove larvae of longhorned beetles (Cerambycidae) from living
> trees. I have not personally observed them feeding on larvae in dead
> trees
> but find it not at all surprising.
>
> Regarding the hypothesis that YTBC may be farming wood-boring insect
> larvae,
> I expect this is not the case. It is well known that stressed trees are
> usually more susceptible to insect attack - particularly borers.
> Therefore,
> after a tree is initially damaged by a borer and maybe by YTBC feeding
> also,
> it has an increased likelihood of further borer attack. This risk is
> enhanced by the open wound created by the YTBC feeding site which is
> likely
> to form a prime oviposition site for other wood boring insects. Clearly,
> the
> feedback loop in this system is likely to lead to an ever increasing level
> of insect damage and can ultimately lead to the death of the tree.
> Following
> death, an even greater diversity of wood boring beetles (often different
> species to those that feed on living trees) will start feeding on the dead
> and decaying tree, thus producing even more food for the YTBC. My
> argument
> is that this is the normal process of tree damage and decay, regardless of
> YTBC feeding. It merely represents a rich food source for a hungry
> cockatoo
> without having to impute active "farming" behaviours.
>
> Michael, I trust this is of interest to the birding-aus audience.
>
> Best wishes,
>
> Rob Floyd
>
> Program Leader, Natural Resources and Biodiversity
> CSIRO Entomology
> GPO Box 1700
> CANBERRA ACT 2601
> AUSTRALIA
> Tel: +61 (2) 6246 4089 Fax: +61 (2) 6246 4155
> URL: http://www.ento.csiro.au
>
>
>
> > > -----Extract from Original Message-----
> > > From: [SMTP:
> > > Sent: Sunday, 28 February 1999 18:37
> > > To:
> > > Subject: Re: birding-aus Yellowtail Black Cockatoos
> > >
> > >
> > > Moving closer to the point of this message, I watched a YTBC extract
> > > several
> > > grubs from that particular Silver Wattle at the time when
> > the damage was
> > > caused. About a year later, I found YTBC's successfully
> > extracting grubs
> > > from the remains of the same tree, exploiting both the
> > fallen branches and
> > > the still-standing stump. This was the third time I had
> > seen YTBC's do
> > > this,
> > > first getting grubs out of a living tree and later getting
> > grubs out of a
> > > tree they had killed: first time I saw it was at Coranderrk
> > reserve near
> > > Healesville (I forget what the tree was); second time was
> > in our garden,
> > > the
> > > unlucky tree being a Pomaderis. On several other occasions
> > near St Andrews
> > > I've seen YTBC's hunting grubs in Pomaderis or Silver
> > Wattles which showed
> > > clear signs of earlier YTBC damage, though I didn't actually see the
> > > initial
> > > attacks.
> > >
> > > The question that intrigues me is this. Do Yellow-tailed
> > Black Cockatoos
> > > actually farm wood-boring insects? I'm making the
> > assumption here that a
> > > dead tree, or one that has been severely wounded by a YTBC,
> > is more likely
> > > to contain edible grubs than a live healthy tree. Are there any
> > > entomologists out there who can enlighten me on this point?
> > I certainly
> > > have
> > > the field impression that YTBC's feed on previously damaged
> > trees more
> > > often
> > > than would be predicted by chance. I can't prove whether it
> > is the same
> > > individual YTBC's that revisit previously damaged trees,
> > but my hunch is
> > > that this could well be the case. Feedback would be
> > welcome, and if anyone
> > > fancies studying the topic seriously I think they could
> > have a lot of fun.
>
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