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As below: No it does not make sense. In that the
individual bird who is developing that feature is not going to be more
successful than those other individuals that are not developing that feature,
for the reason of benefiting the plant! For a feature to evolve in a species, it
must be of genetic benefit to the individual and its offspring. The possibility
that it may be of benefit to a totally unrelated species, in this case bird /
plant is irrelevant. That is not to say that the feature of baldness in
Friarbirds is not of adaptive significance in some way. It may be that it allows
the birds to feed in sloppy flowers without getting its head gooey and by being
bald it may be a better pollinator and so the trees are advantaged by having
more sloppy flowers thereby attracting more Friarbirds. Yes it is true that
"the birds which perpetuate this, benefit from a healthy and robust
plantation of flowering plants- their main food supply." However there
isn't any way that such a loop can drive evolution. The point being that the
adaptive significance for the bird is what benefits the bird and the adaptive
significance for the plant is what benefits the plant but they can develop
simultaneously.
-----Original Message-----
From:
Greg Oakley <>
To:
Birding Aus <>
Date:
Thursday, 19 September 2002 16:59
Subject: [BIRDING-AUS] Noisy
Friarbird - WHY BARE HEADS AND BILL KNOBS?
Phillip Veerman wrote:
You wrote that
"The knob, and the associated depressions either side of the knob, are
also wonderful collectors of pollen ensuring cross pollination as birds move
between plants." That may be true but that is an advantage to the
plants but hardly of any benefit for the birds. The birds aren't going to
evolve something to benefit the plants, unless it has been of historical
adaptive benefit to the birds that started to develop that
feature.
Hi Phillip,
I have
to agree with David on this - ("The knob, and the
associated
depressions either side of the knob, are also wonderful
collectors of
pollen ensuring cross pollination as birds move between
plants.")
I would have thought that cross pollination
would indeed benefit the birds
as it ensures the continued life-cycle of
the plants they are feeding on.
In other words, the continued
existence of flowering plants is reliant
on cross-pollination. Thus, the
birds which perpetuate this, benefit from a
healthy and robust
plantation of flowering plants- their main food supply.
Does this
make
sense?
Regards,
Greg
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