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RE: woodpecker color



Since Rob challenged me for an opinion, here goes.  But you may not be 
satisfied!

First of all, not all woodpeckers sport red on their heads.  In 
Black-backed and Three-toed Woodpeckers, yellow is the splash of colors on 
the males.  And though I don't know much about woodpeckers worldwide, I 
suspect that there are other species with no red.

And here's another caveat:  "Why?" questions relating to biological 
phenomena are notoriously difficult to answer.  In the trade, such 
speculations are fun to make, but are often pejoratively referred to as 
"arm waving."

(What a killjoy!)

Extensive research on vision in birds has been done, and it is well-known 
that they do see colors. Combine that with evolutionary theories on sexual 
selection (beginning with Darwin and a hot topic ever since).  The notion 
is that males and females chose mates that show signs of good health and 
probably good genes.  It seems that in birds, plumage is often the obvious 
indicator, though singing and other territorial behavior probably play 
roles as well.

Red may have become the signal for woodpeckers, but probably just by chance 
in some early ancestor of all woodpeckers (as Rob has pointed out).  We'd 
have to know more about ancestral species, but unfortunately, feather color 
does not appear in the fossil record.

There is some evidence that redness can be a sign of health in other bird 
species.  For example, the shade of red in adult House Finches seems to be 
related to diet.

As I said, it's fun to speculate, but in evolutionary terms, it's probably 
better to invoke the simplest explanation--namely, a chance occurrence that 
caught the eye of a potential mate and got passed on to future generations.

Meanwhile, enjoy that red.  And spend some extra time trying to see the 
cryptic flush of pink on the undersides of those Red-bellied Woodpeckers 
hanging from your suet feeders!

Norm

At 10:50 AM 2/6/2002 +0000, you wrote:

>Craig A. wrote:
>
>>Anyway, I come back to you with a question.  Does anyone have any 
>>idea >why at least one sex of all the woodpeckers in our area have at 
>>least >some red on their head?  I'm curious to know if there is a 
>>scientific >explanation of this?
>
>Never saw anyone respond to Craig's interesting question (sounds like a 
>good one for Norm Budnitz to me!), so I'll take a stab:

***********************************************************
Norman Budnitz, nbudnitz@duke.edu
919-684-3592 (day), 919-383-0553 (eve), 919-660-7293 (fax)

(work) Biology Dept, Duke Univ, Box 90338, Durham NC 27708
(home) 4115 Garrett Drive, Durham NC 27705

PROGRESS: the victory of laughter over dogma.
(Tom Robbins, Half Asleep in Frog Pajamas)