By Burt Glover
April 28, 2024

Sitting on the porch earlier this week, I watched the cedar waxwings — a large, shape-shifting flock of the birds traveling about the yard, moving from tree to tree in precisely choreographed waves with a seemingly singular purpose, as if they are controlled by some outside force.

One minute, they are mobbing one certain holly tree out back, calling out their thin, lisping cries, “sree?” methodically stripping the tree of its bright red berries. Soon the switch will flip, and they will decide that it’s time to swarm the bird bath, or move to another holly, or maybe they will head over to munch down on the tulip poplar flowers. Sometimes, out of the blue, they will suspend all action, retreating to a nearby pine tree, where they line up perfectly still along the limbs, their silhouettes almost indistinguishable from pine cones.

I searched through a number of online videos to find one that shows the curious waves of movement as cedar waxwings feed. This one does it best. 

Cedar waxwings have such flawlessly smooth plumage, one can’t help making comparisons. Some have likened them to porcelain figurines; others to finely carved wood or to silk. It’s no surprise that their genus name, Bombycilla derives from the Ancient Greek word bombux, meaning “silk.” Head and body colors are a rich palette of tan-brown, lemon-yellow and light blue-gray. Distinctive is the subdued crest on the top of its head and the bold black mask bordered in white across its eyes. The tail is tipped with bright yellow. Most striking are the brilliant red tips on secondary flight feathers of the wings. Males and females are almost identical. 

I was surprised to learn that waxwings do, indeed, have wax wings — well, partially so, anyway. Those stunning red tips are actually flattened appendages on the feathers, colored by a waxy red secretion. The secretion derives from a carotenoid pigment, astaxanthin, which originates from the berries that they eat. The pink and red colors of flamingos, shrimp, salmon, lobsters, and others are due to eating algae that also produce this astaxanthin. Nobody is really sure of the function of those red tips– some speculate that they may play a role in mate selection. The number of these appendages appears to increase with age– individuals with zero to five waxy tips appear to be immature birds, while those with nine or more are thought to be older. Individuals with similar numbers of tips tend to associate as mates.  

The wintertime cedar waxwing diet consists mainly of fruit– lots of fruit, mainly in the form of berries. One author describes them as gluttonous birds, sometimes becoming so engorged as to be unable to fly, and have been known to fall helpless to the ground. Birds examined after a feast of berries were found to have their stomachs and throats full, with even more berries in their mouth waiting to be swallowed.

In early summer, as berries become scarce and insect populations swell, waxwings supplement their diet with insects, such as beetles, larvae, ants, cicadas, and flying insects caught on the wing. Native cankerworms (a type of inchworm, sometimes considered a pest) which feed on many deciduous trees, are a favored food of waxwings and their chicks. A flock of thirty birds could easily eat 90,000 of these in a month’s time. As an aside, it doesn’t take much thought to consider the chain of unintended consequences caused by using pesticides to kill the native worms that are a primary food supply of native birds. 

After hatching, the cedar waxwing nestlings are fed insects for the first few days,then switched over to an almost all-fruit diet.  A diet consisting mainly of fruit would cause most other of our birds to lose weight and eventually die, but the efficient digestive system of waxwings allows them to do so. Holly, mistletoe, dogwood, hawthorn, elderberries, blueberries, mulberries — name a fruit, and waxwings probably eat it.

As mentioned, they do also eat insects. With this being the case, I began wondering why they spend so much time flocking to flowers on our tulip poplar, crabapple and mulberry trees. Are they snatching up small beetle and other pollinators from within the flowers? With a little research, I found that waxwings also eat the flowers, flower stamens,  and catkins on various trees. The pollen in these structures provides the protein that is missing in a mostly-fruit diet. In addition, oxidation of the pollen proteins in their digestive system creates a bicarbonate that serves to buffer the excess acidity of the fruit. 

An especially curious and endearing aspect of cedar waxwings is their highly social and egalitarian nature. With seemingly hundreds of waxwings swarming the one holly tree, you’d expect fierce competition. Not so. They stage in one or two nearby trees and take turns flying to the holly. You’ll see one eat a berry or two, then fly back to the staging tree to make room for another to eat. Cedar waxwings are unique in the bird world for their regular habit of “sharing” berries. As one observer reported, “When the end of a twig holds a supply of berries that only one bird at a time can reach, members of a flock may line up along the twig and pass berries beak to beak down the line so that each bird gets a chance to eat.” As the focus of the flock suddenly changes to a dip and a drink of water, you will likewise see them taking turns at the birdbath. Afterward, they may be seen grooming one another. Such a spirit of cooperation!

Working in the backyard this weekend, it took me a while to notice the uncharacteristic stillness in the trees. Could it be? I waited. By late afternoon, it seemed likely that the cedar waxwings had departed for the year. Interestingly, the white-throated sparrows — their songs drifting in the air throughout the day before — were gone, too. I’ll miss them. Both of these birds are migratory, spending their summers in their breeding grounds in the northern US and southern Canada.

The white-throated sparrows will return like clockwork around November 1st. The cedar waxwing will arrive a bit later, taking their time to return south, as they stop here and there along the way — perhaps for weeks at a time — imbibing on the numerous autumn-ripening berries and teaching their young the ways of the waxwings.