What does the red "waxy" projections on waxwings indicate?

Cedar waxwings.  Notice red "waxy" tips of secondaries (main & inset).  Insert: no "waxy tips".

Waxwings don't actually make wax.  The bright red tips projecting off the secondaries of the wings are actually projections of the feather shafts.  They are actually made of keratin, a structural protein.  The colours come from bright coloured fruits that have deep red pigments (you can see berries in lower left inset image).  The berries contain carotenoids, brightly coloured pigments that are important precursors to certain vitamins and antioxidants.  The particular pigment is called astaxanthin.  These same pigments end up in the projected feather shafts of the waxwings.  If you want to see one on a feather, click here.

There's more.  If you look at the waxwing pair in the lower left inset, you will see that the front one has no such red waxy tips, while the back one does ( you have to look closely).  They are born with no such tips; they develop over time.  Up to nine tips develop over time, and they get longer with each progressive year.  It is thought that these are important indicators to potential mates, demonstrating which individuals have survived the longest and are therefore worthy of mating with.  

The longest tips are found on the males.  I was interested to see how long they could be and found that, at their longest, they could be up to a cm in length.  This would be exceptional as they often range somewhere in the half centimeter mark.

The feathers are occasionally moulted.  The older a bird is, the larger and more numerous the red tips become.

Thanks for reading.

Eric Svendsen     www.ericspix.com

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