On Wed Jul 23, Grant Hendrickson wrote:
>
>If you missed the Attenborough special Wednesday night on Birds of Paradise
>on PBS, you missed a real treasure. Stunning photography and, at least to
>me, amazing colors and behaviors. Set your VCR for Sunday morning, the
>27th, from 2:00 - 3:00 AM on Channel 9 (Seattle) for a rebroadcast. This
>one will go in my permanent file!

I only caught the last half, but watching this show I was
struck by the excessive level of ornamentation in the lives of
these birds.

They are extravagant. They use a lot of energy in their mating
rituals. They use a lot of energy producing elaborate feathers
that serve no purpose other than during mating.

However, they have evolved under the influence of natural
selection. The selective forces have determined that their form
is the fittest, the most efficient.

How to resolve this apparent contradiction? Given that they are
efficient from the point of view of the selective forces around
them, what can we say about those selective forces? I have a
few guesses.

1 whatever selective forces exist now have been more or less
the same for a very long time. The variety of shapes
and colours on the various islands did not evolve over a few
generations.

2 there has been a complete lack of predators for a very long
time. It would not take a very clever preditor to catch
these birds; any reasonably agile rodent could take their
eggs.

3 unsuccessful breeding is important. An elaborate mating
ritual might reduce breeding success, suggesting a stable but
very limited environment, with room for only a few dozen
birds. A more efficient breeding protocol could produce so
many birds the entire population would be at risk.

The variety of outcomes of evolution is wonderful.

Brent

PS The lights dim over Washington and BC as 2AM Sunday as
hundreds of VCRs start taping.

--
Brent Beach, Victoria, BC, CA