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Re: magpie (fwd)



So... I guess the white appearance of the feather
patches is probably due to down protruding from
underneath? Why else would it appear white?

Jason
Wake Forest, NC



On Thu, 18 Jan 2001, Joshua Stuart Rose wrote:

> Date: Thu, 18 Jan 2001 18:40:46 -0500 (EST)
> From: Joshua Stuart Rose <jsr6@duke.edu>
> To: carolinabirds@duke.edu
> Subject: magpie (fwd)
> 
> Hi c-birders,
> 
> An ornithologist from CCU in Conway, SC (former home of Andreas 
> Kristensen, the stringer-slayer) sent me some comments correcting and 
> amplifying what I said about melanins in birds, and the appearance of 
> aberrant white patches in otherwise black birds. For those who are 
> interested, read on...
> 
> Joshua S. Rose
> Duke University
> Department of Biology (Zoology, R.I.P.)
> 
> jsr6@acpub.duke.edu
> http://www.duke.edu/~jsr6/
> 
> ---------- Forwarded message ----------
> Date: Thu, 18 Jan 2001 15:02:25 -0500 (EST)
> From: chris hill <chill@kingfish.coastal.edu>
> To: jsr6@duke.edu
> Subject: magpie
> 
> Hi Josh, 
> 
> I'm not on carolina birds right now, but read it on Jack Siler's page.  
> I'd add two things to your discussion.
> 
> Not only blacks in bird plumage, but also browns, grays, rufous, and buffy
> yellows are all due to melanins, which are found in the plumage of almost
> all birds (not just black ones). In addition, I don't think melanins are
> that expensive to make. They're made from tyrosine (so says Gill's
> ornithology text), a common amino acid.  While there's some metabolic
> cost, I bet it's fairly trivial compared to cost of making the feather
> itself.  Birds that are temporarily starved during feather growth do
> develop a weak spot in the growing feather (aka "hunger trace") but I
> don't remember ever seeing a change in feather color around the hunger
> trace.
> 
> I've been seeing the occasional crow with white wing patches since my
> teens (twenty years ago).  I was less prudent than Russ Palmieri - I
> thought "Jackdaw!" on the first one before I thought magpie.  And Jackdaws
> don't even look like that.  Although I haven't persuaded many others, I
> think in many cases what appears to be white feathers are often more
> transparent than white (I've seen blue sky through one white wing patch).  
> I've wondered if crows might be more prone to particularly vigorous
> feather parasites.  The effect might be exaggerated if the parasites went
> for the more pigmented areas first.
> 
> A point in favor of the parasite hypothesis would be if more
> "white-winged" crows turned up in summer (i.e., when the flight feathers
> are oldest, before the August molt).  Russ's bird doesn't fit that
> pattern, most of mine do, but I haven't collected reports systematically.
> Of course, capturing a couple would help define the cause, too (good
> luck!!).
> 
> Chris
> 
> 
> **************************************************************************
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> 
> 

_______________________________________
                                                     
     Jason A. Sircely                         
     Department of Biology               
     Box 90338                                
     Duke University                         
     Durham, North Carolina 27708   
     Tel: 919-684-2267                           
                                               
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