As far as I can see, the rule of thumb for evolution is that organisms
that are better suited to the environment they exist within are more
likely to survive to sexual maturity and hence tend to produce more
offspring. The rub is that in the case of species with sexual
dimorphism, the gender making the decision doesn't always make its
decision on the basis of characteristics that enhance an individual's
survivability [eg excessively long tails, predator-attracting colours
etc].
The thing that is unusual about Eclectus Parrots is that the brooding
gender is the brightly coloured one. I think there are a couple of
dimorphic species where the male does the breeding and is less
conspicuous - eg Plains Wanderer?
Ultimately you could say that Eclectus Parrots are unconventional - a
bit like people who misplace apostrophe's.
Regards, Laurie.
On 12/05/2008, at 11:33 PM, Philip Veerman wrote:
I too liked that doco and all the raptor bits as well. But no need
for me to at this late stage add to what others have mentioned. The
one thing that I didn't like though was the statement made that the
Eclectus Parrot "breaks all the rules of evolution". That is a
nonsense. There are an infinite number of "rules of evolution" that
relate to every feature of every organism: genetics, physiology,
biogeography, structure, behaviour, all the rest. The Eclectus
Parrot adheres to them as much as everything else. The point they
were making is that the bird appears to contradict only one "rule",
which is only a general trend, as there are many other species that
outwardly show the same aspect, albeit for different reasons. That
relates to the reversed sexual dimorphism (brighter coloured
females). Having made that wrong remark, they then proceeded to
outline why it is not true, the particular nesting behaviour of the
bird allows that difference. The bird is indeed not breaking that
"rule of evolution". It is just that it has adopted a particular and
unusual strategy that allows it to adhere to the rule in a different
way from most birds. It is damaging to suggest in such loose manner
that any organism "breaks any of the rules of evolution" because the
comment can easily be taken out of context. It is simply that we
should not take the unusual adaptation as somehow being inconsistent
with the well documented trend without properly seeing the evidence.
Philip
www.birding-aus.org
birding-aus.blogspot.com
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