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Well - I had to think about the coloration of the bill and lores for a 
minute or two.  The juveniles are more drab in the coloration of the 
gular pouch - paler color than the adults.  Their bills will also be 
more black.  Adult bills seem to get lighter as they age - more worn.  I 
don't think the bill and lore color would work that well, but I could be 
wrong on this.  I found a way to determine if a cormorant was a juvenile 
for my purposes.  I looked inside of their mouth and at their eyes.  
Early in the breeding season adults have a bright blue (almost cobalt 
blue) mouth.  This coloration fades through the summer.  The juveniles 
have a gray mouth - no blue at all.  Adults have a bright green eye, and 
juveniles have a gray eye.  I used the combination of these colors.  
But, I was either capturing the cormorants or shooting them as part of a 
diet study.  So I had them all in hand.  I don't think these 
characteristics help when looking at them through a scope or 
binoculars.  Sorry.

Adam



> Date:    Fri, 10 Aug 2007 09:28:44 EDT
> From:    -  Maeve Kim <[log in to unmask]>
> Subject: more on cormorants
>
> Thanks, Adam, for your fascinating and informative post about cormorants. Now 
> I want to look at cormorants more closely; I'd love to see the "leapfrog" 
> behavior!
>
> I estimated that many of the birds in the raft I saw were juveniles because 
> of the large amount of yellowish-orange near bill and lores, rather than the 
> light breast. Is the bright color a good indicator?
>
> Maeve Kim
> Jericho Center