Both Cedar and Bohemian Waxwings derive their common names from the red, waxy tips of some of their secondary feathers. The color of this wax is due to the presence of the pigment astaxanthin. Ornithologists used to theorize that these red tips protected the feathers from wear and tear, but this has not been borne out in studies.
What has been established is that the red appendages increase in both number and size with a bird’s age. Immature birds usually have 0 – 6 waxy tips. Older birds have more than nine. The number of tips appears to function as a signal of age and status in mate selection; individuals within these two age categories choose each other as mates. It also turns out that pairs of older birds (with high numbers of red tips) tend to nest earlier than younger birds. They also have larger clutches and fledge more young than younger birds with fewer waxy tips.
An easy-to-see cue such as these red feather tips that indicate age, maturity and social status at a glance would be very useful in species such as Cedar and Bohemian Waxwings that are often found in large flocks.
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