Flocks of hundreds of cedar waxwings descended on Sewanee this week. They travel in nomadic groups, searching for sugary fruits. Unlike most birds in our region, waxwings feed almost exclusively on fruit for much of the year. In Sewanee, they are sporadically common in the spring and fall, but very scarce in summertime. Most of the birds that are here this week will move north and east to breed. Look for them perched in tight clusters in the treetops or fluttering around fruiting shrubs.

The waxwings’ high-pitched calls (up to 8kHz, nearly twice as high as the highest piano note) are distinctive, but they test the limit of our hearing. For many people, the calls are inaudible except at close range when the sound gets loud enough to cross the ears’ detection threshold. As we age, we naturally lose hearing in the high range, although this can be accelerated by exposure to loud noise (earplugs are a naturalist’s best friend…).

Waxwings are named for the tiny red “flags” on the end of some of their wing feathers. Although these little flags look like wax, they are made of the same material, keratin, as the rest of the feather, infused with red pigment. Young birds have fewer flags, so these red marks may act as social signals through which older birds can avoid breeding with inexperienced youngsters. Older birds have higher breeding success, so it is to their advantage to stick together.

The yellow bar across the end of the waxwings’ tails is also produced by a pigment in the feathers. Over the last forty years, waxwings with orange-banded tails have appeared, especially in the north-eastern parts of the continent. At first, scientists speculated that this was a new mutation, spreading through natural selection. Further study showed that no genetic change was involved. Instead, the waxwings were feeding on the fruits of an invasive plant, Morrow’s honeysuckle, that contained orange pigment. If a molting waxwing feeds on this honeysuckle, the new feathers will pick up the orange pigment. In addition, all the fat in their bodies gets stained. I think of waxwings every time I see someone sucking on a blue slurpee. Surely their insides must be turning blue; maybe the hair will follow.

The photos on this page show the various ways that the waxwings use their silky crests to signal to each other — flat, cocked, and spiky. This expressiveness, combined with their eye-bands and overall silky plumage makes them one of the sharper-dressed birds in our region. Classy.

My account draws on information in: Witmer, M. C., D. J. Mountjoy and L. Elliot. 1997. Cedar Waxwing (Bombycilla cedrorum), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology. doi:10.2173/bna.309  The lead author on this paper is Mark Witmer, a colleague from grad school. He showed me the orange insides of a waxwing once — very cool.