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Re: Canada's WWD website



Ti... I mean, Tom Holtz wrote of the Canadian Discovery Channel website:

> The dino hunter page has profiles on various workers such as Currie,
> Russell, Feduccia, Sues, Brett-Surman, and yours truly.

Since Tom is too shy to point out instances of himself in the media
I'd also like to draw your attention to the April 7 issue of _Science_
which features quotes of Honored Person Holtz in a discussion of
"Walking With Dinosaurs".  Honored Person Holtz virtually spars with
Pontentially Honorable Person Norm MacLeod (owner of the PaleoNet
mailing list) who wasn't quite as pleased with WWD.  There wasn't much
there that we haven't already seen here and on VRTPaleo, but if (like
me) you have a wall dedicated to Honored Person Holtz, you'll want to
clip out this article and post it prominently.

In other news, Sam (posting under the pseudonym of Martin Barnett)
wrote:

} I noticed that all the birds' feathers (with the possible exception
} of Pernis aviporus, the honey buzzard) were of the following
} colours:
} 1.    Black
} 2.    White
} 3.    Grey-scale
} 4.    Anywhere within the brown spectrum between peach and terra-cotta

I would like to extend that down into the UV.  Measurements that I and
others have made indicate that the reflectance spectra of raptor
feathers are flat down to around 300 nm.  That is, if a feather has
high reflectance in the human-visible spectrum (e.g., like the snowy
owl) then it also has high-reflectance in the UV.  If it has low
reflectance in the human-visible spectrum (e.g., like Harris' Hawk) it
has low reflectance in the UV as well.  Neither of these conditions
are necessarily true since some birds with "black" feathers are
actually UV-bright, and others with "white" feathers are UV-dark.

The general thinking about this sort of thing is that animals tend to
use neutral colors (i.e., flat reflectance spectra -- a reflectance
spectrum is a plot of the amount of light reflected as a function of
wavelength) as an aid to crypsis.  If you reflect all wavelengths
equally then the light reflected off of you has a spectrum with the
same shape as the light illuminating you (the shape to which I refer
here is a plot of the energy or quantal flux vs. wavelength).  If
instead you have a peak or trough in your reflectance spectrum then
the light reflected off of you will tend to have that same peak or
trough irrespective of the shape of the illumination spectrum.  The
latter case generally makes detection and identification easier, and
hence is generally avoided by animals whose lifestyles depend upon
their being inconspicuous.  As in all of biology, things are more
complicated than that since animals also have to worry about the
reflectance spectra of the objects that frequently surround them and
the shapes of the illumination spectra they generally encounter.
However, drab coloration is generally better than gaudy colors if you
want to be inconspicuous.  How well that generalization would hold for
dinosaurs is anyone's guess since, of course, tigers look downright
garish to us...

-- 
Mickey Rowe     (rowe@psych.ucsb.edu)