the walk of shame for Orange-bellied Parrots

To: <>, <>, <>, <>
Subject: the walk of shame for Orange-bellied Parrots
From: Simon Mustoe <>
Date: Sun, 25 Jul 2010 07:24:07 +0000

I'd be interested to know more about what background information there is. 
Whilst I would normally whole-heartedly agree, the theory may not apply to OBP 
at present. As I understand it, the species has in the past, been quite fecund. 
It was not unusual to have 4-5 chicks fledge per adult but the population 
either remained the same / declined year to year. So for many many years, it 
has been clear that habitat change at the wintering grounds is the driving 
factor behind loss of the population.

So if we now have a situation where the birds are barely laying, will this mean 
lowered fecundity in any future year? If over-winter mortality remains 
consistent, then this would mean a reduction in the population - there being 
less redundancy in the number of young. As you say and as Peter Menkhorst 
rightly pointed out, the viability of wild populations depends more on adult 
survivorship. However, this is only a 'model-based' assumption and is only 
correct when the population is large or it is extrapolated out over long 
periods of time. Population viability models / theory doesn't apply very well 
to small populations or short-term scenarios because this makes populations 
very prone to short-term or unexpected stochastic variation. Read the 
assumptions behind any PVA and always the same warnings appear.

So whilst I agree with the theory, I don't agree that we can assume that 
removal of young is not going to have an impact. It's a great point you raise 
though and it would be brilliant to get some further insights.



> From: 
> To: ; ; ; 
> Subject: RE: [Birding-Aus] the walk of shame for Orange-bellied Parrots
> Date: Sun, 25 Jul 2010 00:43:57 +1000
> hey all
> A small point on the removal of chicks as a strategy for improving the
> survival of the species. I don't know but I suspect that pulling
> chicks from a nest will have no impact on the eventual total wild
> numbers.
> This is because animals are being removed from the population when
> they are at their most vulnerable and dispensable (to the population).
> Based on other species, I'm guessing that if more than a third of OBP
> that hatch successfully reproduce themselves that would be an
> extraordinary thing.
> In most species the population looks something like a triangle, with
> animal that start dying at an alarming rate once they reach
> independence. I imagine, although I don't know, that the OBP is no
> different. Taking animals that would have almost certainly died anyway
> isn't likely to be a huge loss for the population.
> It's just a shame that while pulling chicks may reduce food completion
> in the nest, it won't also remove the dangers of habitat destruction,
> cars, raptors (who have to eat) and the various other dangers that
> will take care of most of the rest of that age cohort.
> I'm guessing that although the numbers look and sound large, the
> impact to the wild population will be irrelevant while the impact to
> the captive population will be priceless.
> cheers
> storm

We want to hear all your funny, exciting and crazy Hotmail stories. Tell us 
To unsubscribe from this mailing list,
send the message:
(in the body of the message, with no Subject line)
<Prev in Thread] Current Thread [Next in Thread>

The University of NSW School of Computer and Engineering takes no responsibility for the contents of this archive. It is purely a compilation of material sent by many people to the birding-aus mailing list. It has not been checked for accuracy nor its content verified in any way. If you wish to get material removed from the archive or have other queries about the archive e-mail Andrew Taylor at this address: andrewt@cse.unsw.EDU.AU