Why the black beaks

[Rod Wiley]

Every one was asking me why the black beaks on the Gold finches. Here they are at the feeder, as you can see its the feed thats marking up there beaks. Rod

www.rjwileyphoto.com (http://www.rjwileyphoto.com)
www.adayintheswamp.com (http://www.adayintheswamp.com)

[Dan Brown]

So, it's the niger seed! The black seed is doing the staining? This looks like a bird feeder advertisement, but you rarely see Crossbills in ads:D. BTW, the yellow looks hot to my jaundiced eye:p.

[Axel Hildebrandt]

The black beaks are interesting but I'm more surprised you have red crossbills at your feeder. When and where did you make this image?

P.S.: I will move the thread to the behavior forum.

[Rod Wiley]

Last month in Wyoming

[Declan Troy]

Bill color in goldfinches is under hormonal control. During winter it is typically grayish brown but changes to orange/yellow as the birds progress to breeding condition. The change progresses from the base to the tip with a dark tip generally persisting. In parts of their range goldfinches can initiate nesting quite late so I suspect these birds may already have lost some, but not all, of that black. Redpolls do the opposite, their bills get darker in the summer but then most birders don't get to see them during the breeding season.

[Ilija Dukovski]

When it comes to wingtips in seabirds,
my understanding is that the presence of the pigment
melanin makes their wingtips stronger and less prone to wear
(especially in wet conditions). Melanin happens to be black in color
therefore most seabirds have black-tipped wings. Perhaps
the black beak tip in goldfinches is also adaptation to limit the beak tip damage
by enforcing it with melanin