Beccofrusone dei cedri

Identificazione

Cedar waxwings are medium-sized birds approximately 6–7 in (15–18 cm) long and weighing roughly 30 g (1 oz). Wingspan ranges from 8.7 to 11.8 in (22 to 30 cm). They are smaller and browner than their close relative, the Bohemian waxwing (which breeds farther to the north and west). Their markings are a "silky, shiny collection of brown, gray, and lemon-yellow, accented with a subdued crest, rakish black mask, and brilliant-red wax droplets on the wing feathers." These droplets may be the same colour as the madrone berries they are known to eat. These birds' most prominent feature is this small cluster of red wax-like droplets on tips of secondary flight feathers on the wings, a feature they share with the Bohemian waxwing (but not the Japanese waxwing). These wax-like droplets are attributed to the pigmented and medullary layers of the secondary tip being surrounded by a transparent cuticle. The wings are "broad and pointed, like a starling's." The tail is typically yellow or orange depending on diet. Birds that have fed on berries of introduced Eurasian honeysuckles while growing tail feathers will have darker orange-tipped tail-feathers. The tail is somewhat short, and square-tipped. Adults have a pale yellow belly. The waxwing's crest often "lies flat and droops over the back of the head." It has a short and wide bill. The waxwing's black mask has a thin white border. Immature birds are streaked on the throat and flanks, and often do not have the black mask of the adults. Males and females look alike.<p>The flight of waxwings is strong and direct, and the movement of the flock in flight resembles that of a flock of small pale European starlings. Cedar waxwings fly at 40 km/h (25 mph) and fly at an altitude of 610 m (2,000 ft).<p>Cedar waxwings are also known as the southern waxwing, Canada robin, cedar bird, cherry bird, or recellet.<p>The oldest observed cedar waxwing was eight years and two months old.<p>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. Its call can also be described as "high, thin, whistles." They call often, especially in flight.

Tassonomia

Nome scientifico

Bombycilla cedrorum

Autorità

Vieillot, 1808

Ordine

Passeriformi

Famiglia

Bombycillidae

Genere

Bombycilla

Areale e habitat

Preferred habitat consists of trees at the edge of wooded areas, or forests, especially those that provide access to berry sources as well as water. They are frequently seen in fruiting trees. Waxwings are attracted to the sound of running water and like to bathe in and drink from shallow creeks. In urban or suburban environments, waxwings often favour parkland with well-spaced trees;golf courses, cemeteries, or other landscaping with well-spaced trees; bushes that provide berries; and a nearby water source such as a fountain or birdbath. Also look for them near farms, orchards, and gardens, particularly those with fruiting trees or shrubs.<p>Outside the breeding season, cedar waxwings often feed in large flocks numbering hundreds of birds. This species is nomadic and irruptive, with erratic winter movements, though most of the population migrates farther south into the United States and beyond, sometimes reaching as far as northern South America. They will move in huge numbers if berry supplies are low. Rare vagrants have reached western Europe, and there are two recorded occurrences of cedar waxwing sightings in Great Britain. Individual Bohemian waxwings will occasionally join large winter flocks of cedar waxwings.

Migrazione

Complete migrants

Comportamento

Cedar waxwings are sociable, seen in flocks year round. They are non-territorial birds and "will often groom each other." They move from place to place depending on where they can find good sources of berries.<p>Mating season for this bird begins around the end of spring and runs through to late summer. The male will do a "hopping dance" for the female. If she is interested, she'll hop back. 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. 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. 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. Both parents build the nest and feed the young. Typically, there are one or two broods during the mating season. Young leave the nest about 14 to 18 days after hatching.<p>Cedar waxwings eat berries and sugary fruit year-round, including dogwood, serviceberry, cedar, juniper, hawthorn, and winterberry, 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. They sometimes fly over water to catch insects. The cedar waxwing is sometimes responsible for significant damage to commercial fruit farms and thus can be considered a pest, especially because it feeds in large groups.<p>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.<p>Sometimes, cedar waxwings will eat fruit that is overripe and has begun to ferment, intoxicating the bird.<p>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 live on fruit alone, while other fruit-eating passerines found subsisting on fruit alone to be fatal. Reliance on primarily fruit alone occurs until fruit cessation in the spring when the birds start to feed on insects and flowers. In such cases intestinal analysis revealed stomach contents of 84% fruit, 12% invertebrates, and 4% flowers, among 212 individuals involved in the study.<p>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). 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.<p>Even though waxwings displayed efficient rates of digestion, they also exhibited relatively quick passage rates that are indicative of their low utilization efficiency (36.5%) as fruit skins appeared undigested in feces. 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 suggest the important role they may play in seed dispersal.<p>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 more slowly through the digestive tract. A positive correlation between seed defecation and fruit consumption is seen as rates of ingestion increased only when rates of seed processing also increased. 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. 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.<p>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. 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 on a predominately fruit-based diet.

Conservazione

Waxwings are evaluated as Least Concern on the IUCN Red List of Endangered Species. Populations are increasing in their range partly because fields are being allowed to grow into forests and shrublands, and fruiting trees like mountain ash are being planted as landscaping. On the other hand, cedar waxwings do sometimes crash into windows, and get hit by cars while foraging along roadsides.

Tendenza della popolazione

rising