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From: Peter Stettenheim [mailto:[log in to unmask]] 
Sent: Friday, May 21, 2010 11:01 AM
To: [log in to unmask]
Subject: "Rusty" woodpeckers


Please send this to the UV Birders:

Joanne Norton asked if diet might be responsible for the rusty brown
coloration of a Hairy Woodpecker she's been seeing. I doubt it.  Without
sampling and analyzing a feather, one can't tell whether the color is
produced by a melanin pigment (which the bird can synthesize) or a
carotenoid pigment (which it can't). The first is more likely. The diet of
these woodpeckers in spring is insects and insect larvae, neither of which
would provide precursor carotenoid. Also, these birds aren't molting and
replacing their body feathers at this time of year, the only way that diet
can change coloration. I think it unlikely that the bird belongs to the
western subspecies or she'd have seen it before now. Accordingly. I think
Art Mudge is correct in surmising that the color comes from the wood lining
of the bird's nest cavity. I'm reminded of a population of brownish Sandhill
Cranes in southern Michigan that was thought to represent a distinct
subspecies until the color was found to come from iron-tinted water in the
marshes where they lived.


Peter Stettenheim
168 Croydon Turnpike
Plainfield, NH 03781-5403
603-448-4655 


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