Cedar waxwing

The two common calls of these birds include very high-pitched whistles and buzzy trills about a half second long often represented as see or sree.[9][11] Its call can also be described as "high, thin, whistles."[6] They call often, especially in flight.[9]

Egg, Collection Museum Wiesbaden

Mating season for this bird begins around the end of spring and runs through late summer.[10] The male will do a "hopping dance" for the female. If she is interested, she'll hop back.[10] During courtship the male and female will sit together and pass small objects back and forth, such as flower petals or an insect. Mating pairs will sometimes rub their beaks together. The nest is a loose open cup built with grass and twigs, lined with softer materials and supported by a tree branch averaging 2 to 6 m (6.6 to 19.7 ft) above ground but, at times, considerably higher. It takes around five or six days for the female waxwing to build the nest and can take up to 2,500 trips back and forth. Sometimes the female will steal nest material from other species' nests.[9] The outer diameter of the nest is approximately 12 to 16 cm (4.7 to 6.3 in). Usually 5 or 6 eggs are laid and the female incubates them for 11 to 13 days.[9] The eggs are oval shaped with a smooth surface and very little, if any, gloss. The egg shells are of various shades of light or bluish grey with irregular, dark brown spots or greyish-brown splotches.[9] Both parents build the nest and feed the young. Typically, there are one or two broods during the mating season.[9] Young leave the nest about 14 to 18 days after hatching.[9]

Feeding on tree sap

Sharing a berry

Eating berries

"Red wax" on wing tips visible

Cedar waxwings eat berries and sugary fruit year-round, including dogwood, serviceberry, cedar, juniper, hawthorn, and winterberry,[6] with insects becoming an important part of the diet in the breeding season. Its fondness for the small cones of the eastern redcedar (a kind of juniper) gave this bird its common name. They eat berries whole.[6] They sometimes fly over water to catch insects.[6] The cedar waxwing is sometimes responsible for significant damage to commercial fruit farms and thus can be considered a pest,[13][14] especially because it feeds in large groups.[15]

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.[16]

Sometimes, cedar waxwings will eat fruit that is overripe and has begun to ferment, intoxicating the bird.[9]

Cedar waxwings are a highly specialized frugivorous species, exhibiting almost full reliance on sugary fruits, unlike other fruit-eating passerines that exhibit only opportunistic frugivory when other food sources are in poor supply. Their efficient digestion of fruits containing simple sugars allows them to persist off of fruit alone, while other fruit-eating passerines found subsisting on fruit alone to be a fatal task.[17] Reliance on primarily fruit alone occurs until fruit cessation in the spring when the birds start to feed on insects and flowers in which an intestinal analysis revealed stomach contents of 84% fruit, 12% invertebrates, and 4% flowers, among 212 individuals involved in the study.[18]

Despite the advantage of frugivorous specialization, they did lose body mass when experimentally fed one fruit type alone (Viburnum opulus), but gained body mass when fed pollen-rich catkins as well (Populus deltoides).[19] Many fleshy fruits are energy rich, however, they are deficient in nitrogen (protein) levels required by cedar waxwings (1.7%). The nutrient deficit of sugary fruits alone is mitigated through flower and subsequent pollen consumption that is rich in protein. This response to food diversity illustrates the importance of multiple food sources in order to acquire the precise nutrients needed to maintain bodily metabolism.

Even though they displayed efficient rates of digestion, they also exhibited relatively quick passage rates which are indicative of their low utilization efficiency (36.5%) as fruit skins appeared undigested in feces.[20] The low utilization efficiency of fruits digested by Cedar Waxwings not only indicates the necessity of consuming large quantities of fruits, but viable seeds found in feces also suggests the important role they may play in seed dispersal.[20]

The presence of seeds in feces is also indicative of the digestive limitations associated with eating seed-rich fruits, specifically fruits laden with smaller seeds that pass much slower through the digestive tract.[21] A positive correlation between seed defecation and fruit consumption is seen as rates of ingestion increased only when rates of seed processing also increased.[21] Studies have shown that when seeds were observed being regurgitated or expelled, activity and ingestion increased as opposed to when seeds were consumed and passed through the digestive tract, limiting further activity and foraging in which waxwings exhibited a period of “loafing” characterized by stretches of inactivity after a meal.[21] This limitation of fruit processing poses potential issues for Cedar Waxwings observed consuming nutrient-poor fruits and their seeds as the ingestion of seeds prevents them from increasing consumption efforts to mitigate this low-quality diet.

Ingestion of seeds by cedar waxwings is alleviated via efficient rates of seed processing in which seeds are separated from and defecated before the pulp of the fruit.[22][21] This allows them to still exhibit relatively high digestion efficiencies in spite of the gut processing limitations that are associated with eating seeds. The digestive strategies employed by these birds allow them to subsist off of a predominately fruit-based diet.